License Adjustment

[isaiahdahl]

We should probably formalize the licensing arrangement we've been operating under
for use in ourmobile/web app - just good housekeeping as we move forward.

Can you create a commit to this repo adding something like this: to a LICENSE-DUAL file.

Additional License Grant for PraiseCharts Publishing, Inc.

In recognition of PraiseCharts' ongoing contributions 
and support of ChordsheetJs, PraiseCharts is granted 
permission to use ChordsheetJs under MIT license terms.

This grant:
- Applies only to PraiseCharts Publishing, Inc.
- Requires all modifications to ChordsheetJs source code 
  to be contributed back under GPL2
- Does not extend to subsidiaries or transfers without 
  explicit agreement

Martijn Versluis, Copyright Holder