README: move explanation of ranging & monitoring to Estimote Community Portal.
README: move explanation of ranging & monitoring to Estimote Community Portal.

Link: https://community.estimote.com/hc/en-us/articles/203356607-What-are-region-Monitoring-and-Ranging-
pcdamazo/Android-SDK,SmartDust/Android-SDK,pwittchen/Android-SDK-Estimote,analistacarlosh/Android-SDK,Kaiseryang1224/Android-SDK,DESHRAJ/Android-SDK,lamiastella/Android-SDK,jango2015/Android-SDK,hakimlame94/Android-SDK,nikhilJain17/Android-SDK