Use bundler to install executable

[brysgo]

1. This would allow us to add dependancies to betty.
2. This would allow us to use a more standard workflow of working straight off of master.

I know it is easy to get carried away with dependancies, but there are some that would be nice to have. For instance, https://github.com/mdeiters/semr would allow us to clean up our regular expressions without adding the needless complexity involved with writing our own parser.

[johnku1]

What would steps would we have to go through to get bundler to install Betty?

[pickhardt]

Agreed, this is something that will be good in order to include dependencies well.

[brysgo]

@johnku1 - A potential resource for learning about binstubs installed by gems: https://github.com/sstephenson/rbenv/wiki/Understanding-binstubs