Rapidtide

* (rapidtide) Gracefully handle refinement failure.
* (happy) Fixed some output timecourse naming.
* (atlastool) Major fixes to functionality with 4D template files.
* (aligntcs, applydlfilter, pixelcomp, plethquality, resamp1tc, showstxcorr, showxcorrx) Fixed matplotlib backend initialization to allow headless operation.
* (package) General cleanup and rationalization of imports. isort now used by default.
* (package) Dropped support for python 3.3-3.5
* (package) Fixed a stupid bug that surfaced when reading in all columns of a text file as input.
* (package) Merged tsalo's PR starting transition to new logging output.
* (package) Fixed environment for py39 testing.
* (package) Started to phase out sys.exit() calls in favor of raising exceptions.
* (rapidtide) Corrected BIDS naming of intermediate maps.

* (package) Python 2.7 support is now officially ended. Cleaned out compatibility code.
* (package) Made pyfftw and numba requirements.
* (docs) Wrote general description of text input functions, enhanced description of happy, include examples.
* (style) Began effort with T. Salo to address linter errors and generally improve PEP8 conformance - remove dead code, rationalize imports, improve docstrings, convert class names to CamelCase, use snake_case for functions.
* (showtc) Converted text inputs to standardized code.

* (showxcorrx) Significant cleanup for maximum flexibility and utility.
* (showxcorr) Renamed to showxcorr_legacy
* (linfit) Renamed to polyfitim to better reflect it's function.
* (histnifti) Major upgrade to functionality.
* (showxcorrx, atlasaverage, happy2std, rapidtide2std, spatialfit, applydlfilter, plethquality, histnifti) Moved to argparse.
* (package) Updated all headers and copyright lines.

* (package) Trimmed the size of the installation bundle (really, truly, correctly this time).

* (package) Trimmed the size of the installation bundle (maybe even correctly this time).

* (package) Trimmed the size of the installation bundle.
* (various) Cleaned up imports and unresolved references