Simply ignore all of the root bin/ dir
vcfdistance: Use correct tag name in usage output
vcfdistance: Failing tests for various edge cases

vcfdistance was broken from the start when it comes to small numbers of
variants.  It also always double-added the distance tag to the
penultimate variant line.
Handle VCFs with no variant calls

Previously the #CHROM header (the last line read when parsing headers)
was parsed as a variant line when it was the last line in the input
(e.g.  when there are no variant lines).  This could lead to doubled
up #CHROM lines.
vcfdistance: Correctly handle various edge cases

Tests added in previous commit now pass.

Diff best viewed with whitespace ignored.
vcfdistance: Additional tests for multiple references
Merge branch 'vcfdistance-bugs' of https://github.com/tsibley/vcflib into tsibley-vcfdistance-bugs

Conflicts:
	.gitignore
Merge branch 'tsibley-vcfdistance-bugs'