Fix two installation quirks

[luizirber]

• Quirk 1: doc/requirements.txt forced setuptools==3.4.1, which is super old and breaks installations inside Anaconda (sometimes)

• Quirk 2: pip sometimes fails because it can't find a easy_install.pth inside the Anaconda site-packages (makes sense, no conda package should be installing it), and apparently the fix is to use the --ignore-installed flag. Source

• Is it mergeable?

• make test Did it pass the tests?

• make clean diff-cover If it introduces new functionality in
  scripts/ is it tested?

• make format diff_pylint_report cppcheck doc pydocstyle Is it well
  formatted?

• 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?

• Do the changes respect streaming IO? (Are they
  tested for streaming IO?)

• Is the Copyright year up to date?

[luizirber]

Ready for review and merge @standage @betatim

[standage]

LGTM. Will merge when CI build completes.