35 defensive html parsing

[ericdbarry]

Issue #, if available:
35

Description of changes:
Two problems trying to use this module on our internal login page - neither of them were coding issues with our page but were instead standard HTML entities not being parsed like they should have been.

I added two tests for the issues I found and then added in the code to fix them.

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

@@          Coverage Diff           @@
##           master     #36   +/-   ##
======================================
  Coverage    98.1%   98.1%           
======================================
  Files           5       5           
  Lines         317     317           
  Branches       42      42           
======================================
  Hits          311     311           
  Misses          3       3           
  Partials        3       3

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

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