Fix issue #21: Refactor Hash Size Warning Logic into Common Module

[susinmotion]

fis issue #21
pull out error handling for too many collisions (table too small) into.init_.

Update tests to accommodate.

In filter abund, no threshold for max collisions listed--defaults to .2
Default is force=False. Force allowed in all places.

• Is it mergeable?
• Did it pass the tests?
• If it introduces new functionality in scripts/ is it tested?
  Check for code coverage with make clean diff-cover
• Is it well formatted? Look at make pep8, make diff_pylint_report,
  make cppcheck, and make doc output. Use make format and manual
  fixing as needed.
• Did it change the command-line interface? Only additions are allowed
  without a major version increment. Changing file formats also requires a
  major version number increment.
• Is it documented in the ChangeLog?
  http://en.wikipedia.org/wiki/Changelog#Format
• Was a spellchecker run on the source code and documentation after
  changes were made?

[ged-jenkins]

Can one of the admins verify this patch?

[ged-jenkins]

Can one of the admins verify this patch?

[ctb]

ok to test

[mr-c]

Jenkins, ok to test

[mr-c]

Jenkins, test this please