fix loading error on mac

[3nids]

See https://stackoverflow.com/a/42991692/1548052

Naming the files with _pb2 at the end seems to be the issue.

Fixes #252

[codecov[bot]]

Codecov Report

Merging #258 into master-qgis3 will not change coverage. The diff coverage is n/a.

@@              Coverage Diff              @@
##           master-qgis3     #258   +/-   ##
=============================================
  Coverage         61.34%   61.34%           
=============================================
  Files                17       17           
  Lines              3384     3384           
=============================================
  Hits               2076     2076           
  Misses             1308     1308

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[mnboos]

• Removed the compat module (because we can stick to Python 3)
• Deleted vector_tile_pb2.py
• Renamed vector_tile_pb2_p3.py to vector_tile_pb2.py

See: c56b6f8ac9dfb216f61d3fb0f5aa5bda1ad78add