Fit runner

[jeffjennings]

Adds a full fit pipeline, enabling the ability to run mpol from the command line

TODO :

• update json files
• get logger working
• test full pipeline
• test figure generation
• test both CPU and GPU support

[iancze]

Closing as out of scope for the v0.3 core library, but may make sense as a pipeline example or other package, per our conversations. Thanks!