Add environment variable support

• Add environment variable support
• Return a failing return code if one of the checks failed
• Roll downstream dependencies

Note: this change bumps the schema version to 3, you will have to change your .checklist.yml files as such.

v0.2.5: Merge pull request #115 from nre-ableton/nre/master/environment

Support setting environment variables

Roll dependencies

This release doesn't change any behavior, it only rolls some downstream dependencies.

Publish from Travis

Merge pull request #41 from wickedchicken/restrict_deploy

Only cargo deploy from one build type

Cargo.toml information for publishing

Merge pull request #39 from wickedchicken/more_updates

Add info to cargo.toml

Dependency rolls

This release just rolls some dependencies and doesn't add any new functionality.

Initial usable release

This adds functionality for automated scripts and properly versions the config file in case the format will be modified later.