Add environment.yml for use with conda env create

[caseyfitz]

Just starting to play around and all of the CLI code is working great!

To streamline the setup even further (but not quite Docker far), I created an environment.yml that enables a one-line install in conda (see updated README). This way you only have one file to update if/as requirements change.

Instead of manually typing out an environment name and installing each requirement, we can now just run

conda env create -f environment.yml

[Kreijstal]

Someone wrote a docker file look at #3