bbfrederick/rapidtide: Checkpoint release (6/20/17)

New release to trigger a Zenodo DOI. Fully tested for python 3.6 compatibility. Added linfit to the distribution. Set a limit of 25 dispersion regressors. Reformatted the documentation somewhat. Added some recipes to the documentation for common use cases. Cleaned up and fixed the resampling code. Minor quality and speed improvement to timeshift. No longer output "datatoremove" to save space. Removed some redundant screen refreshes from tidepool. Reorganized and removed dead code. Changed default mode for calculating refined regressors to "unweighted_average". Synced changes in rapidtide2x to rapidtide