Merge pull request #94 from mitchmindtree/master

Fixed xy_pad issue with non-responsive cursor. Fixes #92.
Upgrade to latest Piston
Merge pull request #96 from bvssvni/master

Upgrade to latest Piston
Fixed compiler warnings
Merge pull request #97 from bvssvni/master

Fixed compiler warnings
Fixes #93, Implements EnvelopeEditor widget with example, other small fixes and cleaning up.