fix URL
update README
implicit ROOT symbol, rename variables, &c.
move grammar loading; fix incorrect escape sequences in regexes
simplify setup.py
add treebank transformations; fix incorrect escape sequences
fix incorrect escape sequences
Faster grammar loading & fragment extraction

- Grammar is now loaded directly from textfile to a compiled Grammar object,               takes seconds instead of minutes
- Fragment extraction is more efficient:
  - Penn style trees are read directly from textfile to Node structs.
  - bitsets describing fragments are now in Python bytes objects                             (both hashable and pickle'ble)
  - Tree representation:
    - Terminals no longer take up a Node (merged with pre-terminals)
    - reversed sort order (now ascending).
    - label attribute is gone (LHS label of production)
  - for exact count extraction, only loop over set bits of bitsets