Updated CMAKE_CXX_COMPILER_ID for clang. Fixes #345

CMAKE_CXX_COMPILER_ID now checks for both Clang and AppleClang
in accordance with cmake version >=3.0
http://www.cmake.org/cmake/help/v3.0/policy/CMP0025.html
Shifted to c++11 version for clang. #344

A lot of warnings and errors were being thrown due to usage c++11
standards. Updating the flag, removes the warnings