Clean Up Parsing TODOs

[ctuguinay]

Clean Up Parsing TODOs

This PR addresses #109.

This small PR includes:

• In regions2d_parser.py, add back .evr to file_name
• In regions2d_parser.py, remove TODO for fid.readlines(). There seem to be too many options for the number of possible values and so a counter in conjunction with fid.readlines() would involve a (somewhat) non-repeating pattern for the counter to increase, and this would be more convoluted than just directly calling fid.readline() multiple times
• In lines_parser.py, add back .evl to file_name
• In lines_parser.py, replaced readline() with readlines()
• In lines_parser.py, added code for raising an error for evl file with too few lines
• For line parsing, added test for too few .evl lines and test data for said test

[codecov[bot]]

Codecov Report

Merging #110 (9d6809b) into main (cdc75c1) will increase coverage by 0.05%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #110      +/-   ##
==========================================
+ Coverage   76.22%   76.28%   +0.05%     
==========================================
  Files          13       13              
  Lines         408      409       +1     
==========================================
+ Hits          311      312       +1     
  Misses         97       97              

Impacted Files	Coverage Δ
echoregions/regions2d/regions2d_parser.py	95.65% <ø> (ø)
echoregions/lines/lines_parser.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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