Update to MediaElement.js version 2.9.1
Bump mediaelement version to 2.6.4 and this version to 0.3.2
It doesn't make sense to have the generator available from within a Rails project, because it updates the mediaelement_rails files. I've refactored it into a Thor task found in mediaelement_rails.thor, which can be executed by calling `thor mediaelement_rails:update`. Check out `thor mediaelement_rails:help update` for more information.