Update pip install guide in README.md
Update pip install guide in README.md

Clarify that the GPU package works with Ubuntu and Windows only - same as in this pip install guide https://www.tensorflow.org/install/pip
yongtang/tensorflow,arborh/tensorflow,aam-at/tensorflow,sarvex/tensorflow,petewarden/tensorflow,petewarden/tensorflow,karllessard/tensorflow,aam-at/tensorflow,aam-at/tensorflow,sarvex/tensorflow,annarev/tensorflow,renyi533/tensorflow,freedomtan/tensorflow,karllessard/tensorflow,karllessard/tensorflow,freedomtan/tensorflow,Intel-Corporation/tensorflow,aam-at/tensorflow,ppwwyyxx/tensorflow,Intel-Corporation/tensorflow,adit-chandra/tensorflow,sarvex/tensorflow,karllessard/tensorflow,jhseu/tensorflow,yongtang/tensorflow,jhseu/tensorflow,gunan/tensorflow,yongtang/tensorflow,jhseu/tensorflow,gautam1858/tensorflow,xzturn/tensorflow,davidzchen/tensorflow,adit-chandra/tensorflow,tensorflow/tensorflow-pywrap_saved_model,karllessard/tensorflow,tensorflow/tensorflow-pywrap_saved_model,renyi533/tensorflow,frreiss/tensorflow-fred,tensorflow/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,annarev/tensorflow,tensorflow/tensorflow,frreiss/tensorflow-fred,yongtang/tensorflow,petewarden/tensorflow,Intel-tensorflow/tensorflow,tensorflow/tensorflow,petewarden/tensorflow,ppwwyyxx/tensorflow,gautam1858/tensorflow,xzturn/tensorflow,ppwwyyxx/tensorflow,frreiss/tensorflow-fred,freedomtan/tensorflow,adit-chandra/tensorflow,annarev/tensorflow,tensorflow/tensorflow-pywrap_saved_model,aam-at/tensorflow,petewarden/tensorflow,frreiss/tensorflow-fred,adit-chandra/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,Intel-tensorflow/tensorflow,aldian/tensorflow,davidzchen/tensorflow,Intel-tensorflow/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,cxxgtxy/tensorflow,renyi533/tensorflow,annarev/tensorflow,renyi533/tensorflow,arborh/tensorflow,davidzchen/tensorflow,annarev/tensorflow,jhseu/tensorflow,gautam1858/tensorflow,Intel-tensorflow/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,karllessard/tensorflow,tensorflow/tensorflow,gautam1858/tensorflow,paolodedios/tensorflow,gunan/tensorflow,paolodedios/tensorflow,Intel-tensorflow/tensorflow,aldian/tensorflow,petewarden/tensorflow,adit-chandra/tensorflow,Intel-tensorflow/tensorflow,arborh/tensorflow,Intel-Corporation/tensorflow,cxxgtxy/tensorflow,adit-chandra/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,adit-chandra/tensorflow,adit-chandra/tensorflow,tensorflow/tensorflow,aldian/tensorflow,ppwwyyxx/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,ppwwyyxx/tensorflow,gunan/tensorflow,sarvex/tensorflow,frreiss/tensorflow-fred,tensorflow/tensorflow,jhseu/tensorflow,yongtang/tensorflow,gunan/tensorflow,jhseu/tensorflow,arborh/tensorflow,davidzchen/tensorflow,aldian/tensorflow,tensorflow/tensorflow-pywrap_saved_model,paolodedios/tensorflow,paolodedios/tensorflow,xzturn/tensorflow,sarvex/tensorflow,arborh/tensorflow,renyi533/tensorflow,gunan/tensorflow,arborh/tensorflow,renyi533/tensorflow,freedomtan/tensorflow,xzturn/tensorflow,gautam1858/tensorflow,petewarden/tensorflow,aam-at/tensorflow,ppwwyyxx/tensorflow,yongtang/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,frreiss/tensorflow-fred,freedomtan/tensorflow,gunan/tensorflow,jhseu/tensorflow,freedomtan/tensorflow,frreiss/tensorflow-fred,tensorflow/tensorflow-pywrap_saved_model,arborh/tensorflow,Intel-Corporation/tensorflow,annarev/tensorflow,frreiss/tensorflow-fred,frreiss/tensorflow-fred,xzturn/tensorflow,xzturn/tensorflow,karllessard/tensorflow,tensorflow/tensorflow-pywrap_saved_model,aam-at/tensorflow,cxxgtxy/tensorflow,aam-at/tensorflow,arborh/tensorflow,aldian/tensorflow,tensorflow/tensorflow-pywrap_saved_model,tensorflow/tensorflow-pywrap_tf_optimizer,gautam1858/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,cxxgtxy/tensorflow,ppwwyyxx/tensorflow,sarvex/tensorflow,Intel-tensorflow/tensorflow,arborh/tensorflow,petewarden/tensorflow,paolodedios/tensorflow,adit-chandra/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,xzturn/tensorflow,petewarden/tensorflow,davidzchen/tensorflow,aam-at/tensorflow,davidzchen/tensorflow,gautam1858/tensorflow,adit-chandra/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,tensorflow/tensorflow-experimental_link_static_libraries_once,aldian/tensorflow,aam-at/tensorflow,gunan/tensorflow,yongtang/tensorflow,gautam1858/tensorflow,Intel-Corporation/tensorflow,ppwwyyxx/tensorflow,aam-at/tensorflow,ppwwyyxx/tensorflow,tensorflow/tensorflow,karllessard/tensorflow,freedomtan/tensorflow,gunan/tensorflow,freedomtan/tensorflow,Intel-tensorflow/tensorflow,Intel-tensorflow/tensorflow,gunan/tensorflow,paolodedios/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,renyi533/tensorflow,frreiss/tensorflow-fred,arborh/tensorflow,petewarden/tensorflow,petewarden/tensorflow,freedomtan/tensorflow,gunan/tensorflow,renyi533/tensorflow,adit-chandra/tensorflow,renyi533/tensorflow,tensorflow/tensorflow-pywrap_saved_model,Intel-tensorflow/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,paolodedios/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,renyi533/tensorflow,aldian/tensorflow,tensorflow/tensorflow,annarev/tensorflow,paolodedios/tensorflow,Intel-Corporation/tensorflow,paolodedios/tensorflow,cxxgtxy/tensorflow,xzturn/tensorflow,renyi533/tensorflow,aldian/tensorflow,davidzchen/tensorflow,davidzchen/tensorflow,ppwwyyxx/tensorflow,paolodedios/tensorflow,petewarden/tensorflow,tensorflow/tensorflow,gautam1858/tensorflow,annarev/tensorflow,freedomtan/tensorflow,annarev/tensorflow,jhseu/tensorflow,aam-at/tensorflow,jhseu/tensorflow,jhseu/tensorflow,sarvex/tensorflow,cxxgtxy/tensorflow,tensorflow/tensorflow-pywrap_saved_model,karllessard/tensorflow,gautam1858/tensorflow,paolodedios/tensorflow,Intel-Corporation/tensorflow,tensorflow/tensorflow-pywrap_saved_model,xzturn/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,cxxgtxy/tensorflow,davidzchen/tensorflow,annarev/tensorflow,xzturn/tensorflow,gautam1858/tensorflow,davidzchen/tensorflow,gunan/tensorflow,xzturn/tensorflow,ppwwyyxx/tensorflow,arborh/tensorflow,frreiss/tensorflow-fred,tensorflow/tensorflow,karllessard/tensorflow,freedomtan/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,yongtang/tensorflow,jhseu/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,frreiss/tensorflow-fred,annarev/tensorflow,yongtang/tensorflow,jhseu/tensorflow,davidzchen/tensorflow,Intel-Corporation/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,gautam1858/tensorflow,ppwwyyxx/tensorflow,cxxgtxy/tensorflow,arborh/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,Intel-tensorflow/tensorflow,davidzchen/tensorflow,gunan/tensorflow,yongtang/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,sarvex/tensorflow,adit-chandra/tensorflow,tensorflow/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,karllessard/tensorflow,yongtang/tensorflow,renyi533/tensorflow,freedomtan/tensorflow,xzturn/tensorflow,tensorflow/tensorflow-pywrap_saved_model