Add Node.path column.  Allows queries based on (unescaped) path.
Fix error in CHANGES, and add migration note.
Fix accidental Python 2.6 breakage.
Attempt to increase maximum index size with MySQL
Revert commit that didn't help with Travis' MySQL :-(
Set length of Node.path to 767 so it fits within MySQL's default constraints.
Disable Node.path index altogheter because some configs (Travis) don't support it
Catch two more edge cases for setting path.

1. Parent (or parent's parent etc) might not be part of object tree yet.

2. Parent might not have a name yet.
Merge pull request #313 from Kotti/path-index

Add Node.path column.  Allows queries based on (unescaped) path.