Fix typo in docs

Instructions how to get Shift/Reduce messages printed (Issue #258)

Method iter_subtrees_topdown added

types of ambiguity.
 - Rewritten along the lines of Elizabeth Scott's parser.
https://www.sciencedirect.com/science/article/pii/S1571066108001497

 - Implement SPPF trees per Elizabeth Scott and Bram van der Sanden's work.
http://www.bramvandersanden.com/post/2014/06/shared-packed-parse-forest/

Allow to passing "rankdir" to lark/tree.py:pydot__tree_to_png

lark/tree.py

shaping. For example, passing "TB" instead of "LR" makes the tree
to be draw vertically instead of horizontally.

https://stackoverflow.com/questions/29003465/pydot-graphviz-how-to-order-horizontally-nodes-in-a-cluster-while-the-rest-of-t

docs: clarify end_column value

I interpreted "the column where the token ends" to mean "a pointer
to the last character in the token", which would be the same as
the start column for a single-character token.

However, that's not what lark actually reports. Reword to clarify
this.

https://github.com/lark-parser/lark/issues/240

Added missing binary files to .gitignore

# Conflicts:
#	.gitignore

Typo in documentation

Fix a small typo

Fix Lark class docstring