Emphasized proper use of reset method in docs.

This is related to waylan/Python-Markdown#305.
Merge pull request #306 from brownhead/master

Emphasized proper use of reset method in docs.
No assertIs in Python 2.6. Fixes #294
Skip a weird PHP test.

I can't make out what this PHP test is trying to accomplish. From my point of view, our output is fine. So we skip this test.
Merge remote-tracking branch 'upstream/master' into master-zds