tests clean up
added base_alphabet to grammar definitions

commit ababc893fcd0612252ee02c90607f82009d31863
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sun Nov 24 21:37:11 2013 +0000

    removed unused code

commit 0e2063a959fc89050e4a032ff16076f097496339
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sun Nov 24 21:36:50 2013 +0000

    deleted maxsize and minsize

commit de0278be1ae0ea44069a4aa832172389ad155707
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sun Nov 24 11:46:19 2013 +0000

    added test for Choice with custom base_alphabet

commit bd84a199cd65712fa425e3640b78ff1c2b264aa1
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sun Nov 24 10:54:23 2013 +0000

    reverted the base_alphabet as arg for checkers

commit fa3c3ac285854dbbec8986cb2e69203ae67f6ace
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sat Nov 23 23:34:17 2013 +0000

    added base_alphabet parameter everywhere

commit e3702df9cdf49d93909418ade0857ec54b0bd953
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sat Nov 23 17:35:04 2013 +0000

    partial test work

commit 1e3ca19f8b024c01e80d2c6b5527c41d9b5f0c49
Merge: 0a86a7b 8363930
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sat Nov 23 17:32:39 2013 +0000

    Merge branch 'master' into 64-lexer-input

commit 0a86a7ba926230d0a0a1b4fed6aec3f40cdef83c
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Sat Nov 23 13:59:09 2013 +0000

    tests for desired features
closes #56
alphabet is now a property
AlphabetListLexer -> ChoiceLexer
lexer returns (string, gd)

Before it only returned the string, making harder to know which grammar
definition was recognized
alphabet is now a BNF property
increased exception verbosity
added test for Sequence
fixes broken tests
renamed generate_valid_sequences to valid_sequences
removes WeightedParser. closes #59 . closes #49
Merge branch 'master' into 61-grammar_first

Conflicts:
	pydsl/Grammar/BNF.py