Fix resource/UI resource/ui casing

Case sensitive filesystems will result in TF2 not reading resource/UI,
but resource/ui works.
LOWER CASE ALL THE THINGS
Merge pull request #8 from Nephyrin/case-fix

Fix resource/UI case confusion breaking non-VPK usage on case-sensitive OS
Merge pull request #12 from TheKins/master

Update fork with upstream commits