Add angular.piwik 1.0.2

This pull request adds the angular-piwik library with the name angular.piwik (to match the naming convention for the angular library for which it is an addon).

It doesn't include an `update.json` file for the library because the repository does not contain a minified version.  If it would still be useful to have an `update.json` (which either excludes all files or includes the non-minified version), let me know and I'll add one.

Thanks,
Kevin