tool to make smaller maps and some cleanups

[j-t-t]

• Wrote a script, make_map_subset.py (in a new tools directory) that will create a smaller geojson file from a larger one by writing all linestrings and points that fall within circle (given by lat/lon and buffer radius) to a new file. This is to make debugging and creating dummy files for tests easier.
• Pulled some functionality out of create_segments into util since I wanted to use the resulting function for some analysis
• Took out a bunch of functions out of util.py that are no longer used, and their corresponding tests
• join_segments_crash_concern had a place where I had previously written a crash_joined shapefile to file for debugging, and that's not used anywhere, so I took that out as well.

[codecov[bot]]

Codecov Report

Merging #186 into master will increase coverage by 0.09%. The diff coverage is 68.08%.

@@            Coverage Diff             @@
##           master     #186      +/-   ##
==========================================
+ Coverage   43.84%   43.94%   +0.09%     
==========================================
  Files          27       28       +1     
  Lines        2796     2806      +10     
==========================================
+ Hits         1226     1233       +7     
- Misses       1570     1573       +3

[terryf82]

This looks great and I'm sure we'll have cause to make use of the new map subset feature many times in the future.

The only change I would have made is to call the final parameter to get_buffer radius instead of buff, as passing a buffer to "get_buffer" seems a bit contradictory, but that's just personal preference.

Ready to merge unless anyone else also wants to review?

[j-t-t]

Updated variable names