Also run our tests
Set Git attributes for BAM files in the repository
Add help command and --version options

Rearrange version.h inclusion -- only bamtk.c should #include version.h
so that only one translation unit needs recompiling due to changes in it.

Separate samtools_version() and hts_version() so that they can be displayed
in a more user-friendly way where appropriate.  (--version-only uses
punctuation other than %s:%s as it's likely to be embedded in executable
paths and ":" is a shell semi-metacharacter.)
Write samtools --help output to stdout