get rid of n² loop in WordNet shortest_path_distance
expose type_check parameter of the logic parser
speed up path computations in WordNet reader

1296 calls to shortest_path_distance for pairs of random nouns
used to take 6.752s, now 5.364s. Subtracting 2.187s to load NLTK
and WordNet, that's 44% off.

The main speedup comes from omitting the sort in _related.
changed _LogicParser, _LinearLogicParser, and _DrtParser back to the non-underscore versions, for easier access by load_parser()
Merge pull request #711 from alvations/develop

Added GDFA Symmetrization for nltk.align
updates for PEP-8 compliance and sphinx documentation
Merge pull request #712 from larsmans/wordnet-paths

WordNet paths
use runtests.py
Add elementtree_indent function, needed by ch11 (was in nltk_contrib/toolbox)
corrected function name in recursive call
de-anonymised _DrtParser and _LogicParser
renamed parse_ methods to read_ or load_, resolves issue 656
standardised environment variable pathnames to third party software
Merge pull request #4 from nltk/develop

Syncing fork with nltk-dev