#11 - add multiple form field names for use with different ADFS versions

[groboclown]

Issue #, if available:
#11

Description of changes:
Keeps the original ADFS form names, and adds in the alternate UserName and Password fields for compatibility with other login forms. Note that this implementation allows for combinations that aren't expected (old + new form names).

Includes a new unit test for checking the alternate names.

This also includes some minor styling updates to allow make prcheck pass.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #39 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #39      +/-   ##
==========================================
+ Coverage    98.1%   98.11%   +0.01%     
==========================================
  Files           5        5              
  Lines         317      319       +2     
  Branches       42       42              
==========================================
+ Hits          311      313       +2     
  Misses          3        3              
  Partials        3        3

Impacted Files	Coverage Δ
awsprocesscreds/saml.py	100% <100%> (ø)	⬆️

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[dhensen]

@JordonPhillips I'm pinging you because you are to be the top contributor.
Can this PR be followed up?