Minor bug fix release

Release Notes

1. Modified to automatically append the basename name of the first argument if the second argument is a directory.
2. Added error checking to verify that the first argument is a file.

Enhanced termcolors to support ANSI 256 color mode

1. Enhanced the termcolors package to support ANSI 256 color mode.
2. Implemented native go cross compilation and added the darwin and linux targets.
3. Updated the docker-linux target to correctly write the executable to bin/linux_amd64/csdiff using the linux_ target.
4. Added the --256 to print the available ANSI 256 color mode colors.
5. Updated the documentation.

Initial Release

1. Initial release and documentation.