Added rich comparisons and __iter__ to _Trie

  see issue #16
Switched to lowlevel iteration in __richcmp__

  Note that the current implementation doesn't compare LABEL_ORDER
Added NodeOrder support to __richcmp__
Removed imap and operator imports
Added Python3.4
Updated README
Merge pull request #17 from superbobry/master

Added rich comparisons and __iter__ to _Trie