astropy/ccdproc: 2.2.0 -- Image combination performance

This release contains some modest improvements in image combination performance. For the best performance, install the bottleneck. With bottleneck installed, median_combine is 2x faster. Changes in this version: Image combination is faster for average and sum combine, and improves for all operations if the bottleneck package is installed. Pixel-wise weighting can be done for sum and average combine. When filtering an ImageFileCollection by keyword value, and not explicitly using a regex search pattern (regex_match=True), escape all special characters in the keyword value for a successful search. Return mask and uncertainty from combine even if input images have no mask or uncertainty. Thanks to all of the people who contributed code, opened issues, and/or provided advice: Timothy P. Ellsworth-Bowers (@tbowers7) and Pey Lian Lim (@pllim) wrote code for this release. Yoonsoo Back (@ysBach) and Simon Conseil (@saimn) provided extensive input on image combination. Issues opened by Yash Gondhalekar (@Yash-10), Michael Kelley (@mkelley), Jane Rigby (@janerigby), and Aayushi Verma (@awesomecosmos) were closed in this release. Rieke Bohemann and Tim-Oliver Husser (@thusser) provided extensive details about issues with median combination which have been addressed in this release.