Major refactor

[hmerritt]

Major refactor

Features

• --match flag for custom regex/glob matcher, to override the default .*/.js$
• Recursively walks path to find all files

Changes

• Refactored CLI from mitchellh/cli into spf13/cobra
• Skips printing title for completion, and version commands, so they can be piped or read directly
• Fixed reactenv erroneously matching variables that start with $
• Enforce deterministic sorting and processing of matches
• Test coverage above 80%