Merge pull request #98 from mitchmindtree/master

Fixes #93, Implements EnvelopeEditor widget with example, other small fixes.
Add Travis CI
Merge pull request #102 from Indiv0/add-travis-ci

Add Travis CI
Add rust-ci
Merge pull request #103 from Indiv0/add-rust-ci

Add rust-ci
Handle new piston InputEvent model, Added basic WIP textbox with example.