Distinguish handle of projections

[McAwesomeville]

This is for issue #19:
mapping.py: Function def _parse_crs(crs) distinguishes the revision/version of pyproj and handles the crs value in a different manner.

[codecov-io]

Codecov Report

Merging #20 (df28899) into master (85665c2) will decrease coverage by 0.12%.
The diff coverage is 12.50%.

@@            Coverage Diff             @@
##           master      #20      +/-   ##
==========================================
- Coverage   92.60%   92.48%   -0.13%     
==========================================
  Files          12       12              
  Lines        2138     2142       +4     
==========================================
+ Hits         1980     1981       +1     
- Misses        158      161       +3     

Impacted Files	Coverage Δ
tilemapbase/mapping.py	84.02% <12.50%> (-0.77%)	⬇️

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