v2.1.0 - New destroy() method and bug fixes
- Another fix for unregistering combos using an array of keys
- Added a destroy method to cleanup a listener. Thanks to smerickson for submitting. Pull request #51
- Fixed compatibility for '-'/'_' and '='/'+' keys in FireFox. Thanks to simonsarris for spotting the bug. Issue #50
- Added spm support. Thanks to sorrycc. Pull request #52