Considers isalhum in pdb_selchain

[joaomcteixeira]

Considers chain options to be valid when str.isalnum() is True.

Solves #39

[codecov]

Codecov Report

Merging #40 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #40   +/-   ##
=======================================
  Coverage   82.07%   82.07%           
=======================================
  Files          44       44           
  Lines        3525     3525           
  Branches      742      742           
=======================================
  Hits         2893     2893           
  Misses        446      446           
  Partials      186      186

Impacted Files	Coverage Δ
pdbtools/pdb_selchain.py	84.61% <100%> (ø)	⬆️

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[mtrellet]

Works fine on my side! Thanks ;)

[JoaoRodrigues]

Seems good to me. Mind adding a test to check this? (A small example with 3 chains, A, a, and B where we select each would work).

[joaomcteixeira]

Added tests for selecting capital chain identifiers, lowercase identifiers and digit identifiers.

@JoaoRodrigues review and merge if appropriate.

[JoaoRodrigues]

Seems good! Thanks for the fix and the tests!