Added priority flag support

Merge pull request #17 from CodeMonkeysRu/release/v0.5

Release/v0.5

Dropped php5.5, added ci integration

Merge pull request #15 from CodeMonkeysRu/cleanup

Dropped php5.5 support, added ci checks for tests and cs

ContentAvailable added

#11

Notifications added

0.2.0

Removed version from composer json for autoupdates