Fix travis badge.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Add license/language badges.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Relax build matrix.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Install happy/alex in travis.

They're needed by haskell-src-exts.

Signed-off-by: Austin Seipp <aseipp@pobox.com>