The result is a much smaller file.

Add:
- missing imports
- __version__ variable

Additionally regenerated json parser example

- Refactored lexer interface into LexerConf
- Lexer now compiles regexps only when used (especially useful for ContextualLexer)
- Lexer now doesn't validate on deserialize (noticable speedup)

TODO: Add docs

Added multi-name-imports to the lark.lark grammar.

Include relative imports and rule rewrite

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

0b10
 ^

* All exceptions are now under exceptions.py
* UnexpectedInput is now superclass of UnexpectedToken and UnexpectedCharacters,
  all of which support the get_context() and match_examples() methods.