Merge pull request #126 from mitchmindtree/master

Switched label and widget_matrix over to the builder pattern (see all_widgets example)
fix(text_box): handle text_box string mutating on Return press
test(text_box): add example/test of mutating callback for textbox
Merge pull request #128 from mitchmindtree/master

Updated to the latest rustc, fixed EnvelopeEditor point picking
Merge pull request #129 from mitchmindtree/master

Fixed behaviour of EnvelopeEditor when adding points
Merge pull request #130 from Ryman/textbox_mutation

Textbox mutation
Upgrade to latest Rust
Merge pull request #132 from bvssvni/master

Upgrade to latest Rust
Switched to GenericEvent

Closes https://github.com/PistonDevelopers/conrod/issues/133
Merge pull request #134 from bvssvni/master

Switched to GenericEvent
Cleaned up all_widgets examples, closes #131