Standalone FILE I/O functions in device_matrix.h
[Bug Fixed] in copy contructor. More test cases.
Add a macro gaurd if there's no host_matrix.
Merge branch 'feature/testing' into develop
Remove color.h/matrix.h from #include.
Add a macro gaurd if there's no host_matrix.
Change return-type of matrix-vector-multi to matrix.

Also add a conversion operator from device_matrix to
thrust::device_vector
Change CUBLAS_HANDLE to singleton.
Move matrix-vector multiplication to arithmetic
Remove device_arithmetic.cu. No more explicit inst.
Merge branch 'feature/more-testing-cases' into develop
Merge branch 'release/v0.9'

Conflicts:
	Makefile
	include/device_matrix.h
	src/device_arithmetic.cu
	src/device_matrix.cu
	test.cu