Added example of usage of the new on() specification. Changed the on() method to allow the specification of a target-selector, when having 3 arguments. Otherwise it behaves like before. The API was not damaged
Fixed issue reported in the https://github.com/entomb/k-ink-interface/pull/8#commitcomment-3476483
Merge pull request #8 from mAiNiNfEcTiOn/master

Modified the on() method.