Fix OSX El Capitan incompatibility, by adding CUDA_LIB_DIR to @rpath of libcaffe.so

[mohamed-ezz]

Fixing dynamic linking issue issues on OSX Elcapitan, reported in #3227 and #2720

[kylemcdonald]

This commit made Caffe build for me on OS X 10.11.1.

Currently the master branch at commit b590f1d gives me this error ./include/caffe/util/mkl_alternate.hpp:11:10: fatal error: 'cblas.h' file not found which is super confusing because there are so many things that could cause Accelerate / cblas.h to not be found.

[shelhamer]

See #3695 for a slightly groomed edition of this change. Thanks for the fix @mohamed-ezz !

[shelhamer]

@kylemcdonald OS X 10.11 seems to have moved the BLAS includes yet again. I don't have the time now to figure out a robust solution but this Makefile.config setting finds it:

BLAS_INCLUDE := /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/Headers