Clarifies how to use gtest as a shared library in README.
Clarifies how to use gtest as a shared library in README.

goby/googletest,goby/googletest,dpull/googletest,osamu0329nakamura/googletest,old8xp/googletest-from-google,Perfexion/googletest,osamu0329nakamura/googletest,BeeswaxIO/googletest,old8xp/googletest-from-google,BeeswaxIO/googletest,dpull/googletest,gclone/googletest,Perfexion/googletest,BeeswaxIO/googletest,osamu0329nakamura/googletest,gclone/googletest,dpull/googletest,old8xp/googletest-from-google,Perfexion/googletest,goby/googletest,gclone/googletest