generic attempt
Updated `README.md`
Updated `README.md`
Renamed `Key` to `KeyType`
Added `AddRelease` and `ReleasePressEvent`
Added `AddInterval` and `IntervalEvent`
Add missing files
Updated `README.md`
Added `Triggered` trait

  The `Triggered` trait can be implemented by event context which can be
  triggered.
Added `CallOnce`
Added docs
Each event context implement `Clone`
Added `AddAny` and `AnyEvent`

  Now one can use `e.any([...]).call(...)`
Updated `README.md`
Merge pull request #33 from Coeuvre/master

Separated rust-event and piston. Used generic key type. Added `CallOnce`, Added `AddAny`