Update from latest 0.6

Trimmed whitespaces and ensured a new line on the end of the file

number add BIN_NUMBER

Without BIN_NUMBER, the following error occurs:
lark.exceptions.UnexpectedCharacters: No terminal defined for 'b' at line 1 col 2

0b10
 ^

Merge remote-tracking branch 'origin/0.7b' into 0.7b

Implement Joop Leo's optimisations for right recursion

We can replace Earley Columns with basic python sets
for improved performance and simplicity.

When using the same parser repeatedly for small parsers we incur
significant overhead by recreating the ForestVisitor each parser.
We can cache the Forest walker and re-use it by making it stateless.
Also, we can use slots for all of the Forest Walkers to reduce
construction delay and function call overhead.

Fix typo in docs

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

Method iter_subtrees_topdown added