Added #offMouseenter, #offMouseleave.
Internal storage of event handler for this methods is incompatible with the other event methods!
Added QUnit tests for #offMouseenter, #offMouseleave.
Updated event variable names in library.
Updated API.md, raised version number.
Refactored events. Updated QUnit tests and api docs.
Implemented new internal methods _AddEventListener/_removeEventListener which are used by other event methods to avoid redundant code.
Changed the order of methods in lib and api docs.
Raised version to 2.6