Silence PEP440Warning by default unless invoking easy_install

Upgrade packaging to 14.5

Add a PEP440Warning to make it easier to silence these warnings

Don't warn on empty non PEP 440 versions

* Normalizes release candidates to 1.0rc1 instead of 1.0c1

Empty versions which are not PEP 440 are more likely to be the
fault of setuptools internals rather than anything a user has done
so these warnings are needless spam in that situation.

Upgrade packaging to 14.4

Add a warning when version is parsed as legacy

This fixes an error where there is a different result for if 2.0.5
is contained within >2.0dev and >2.0.dev even though normalization
rules should have made them equal.

This fixes an error where there is a different result for if 2.0.5
is contained within >2.0dev and >2.0.dev even though normalization
rules should have made them equal.