Add license to gem spec

This patch adds the license to the gem spec file, so that no warning
will be generated during the build. The license string is MIT, to match
the already existing LICENSE.txt file.

Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>
Release 0.0.31

This patch bumps the release number to 0.0.31.

Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>
Merge pull request #57 from jhernand/relase_0.0.31

Relase 0.0.31