Update CiviDiscount

https://civicrm.org/extensions/cividiscount indicates there is a version 3.0 CiviDiscount module, but http://d46.demo.civicrm.org/civicrm/admin/extensions?reset=1 shows the demo site is running v2.6 which indicates it is for 4.5 and is alpha.

This seems to be the most recent version in the https://github.com/dlobo/org.civicrm.module.cividiscount/blob/master/info.xml repo, as it is the code in the master branch. However, there is a 4.5 branch which has a v3.0 stable for 4.5, which corresponds to the v3.0 tag for these lines at least. Unfortunately it does not indicate that is available for 4.6, only 4.5. So I'm not sure where the release compatiblity for both versions as seen at https://civicrm.org/extensions/cividiscount-extension/version-30 is coming from.