bbfrederick/rapidtide: Version 1.9.1 (6/17/20) checkpoint release

Remember what I said about the release? Last checkin before 2.0, blah blah blah? So 2.0 is dragging out longer than expected, so I thought I'd put in another stable point before going to 2.0rc1. THIS is the last release before 2.0. Here are a collection of things that I thought should be out in a stable release. (all): Documentation improvements. (all): Many internal changes to support future argument specifications. (all): Backported bugfixes from the development version. (rapidtide2x) Fixed specification of timerange. (docker): Fixed an incompatibility in versions between pyfftw and scipy (thank you to Niranjana Shashikumar for reporting the bug and providing the solution!) (docker): Improved container labelling. (docker): Cleaned up container build. (tidepool): Various fixes and improvements backported from the development version