Add IB support with IB_DESIGNABLE.
Update podspec.
Don't allow ratings less than 1 or more than maximum

Previously it was possible to get `rating` greater than `numberOfStars`
by using the pan gesture recognizer. This commit boxes `rating` between
1 and `numberOfStars`
Merge pull request #7 from neilkimmett/master

Don't allow ratings less than 1 or more than maximum
Merged with parent