partial work llkrecursive descent
Merge branch 'master' into llkrecursive_descent
reenabled test
Merge branch 'master' into llkrecursive_descent
Merge branch 'master' into llkrecursive_descent
BNF.first returns a grammar
improved readability of RecursiveDescentResultTree
using Sequence instead of RecursiveDescentResultTree #49
fixes infinite recursion error
improves first_lookup readability
using grammars definition for first_lookup
moved Alphabet to Grammar
renamed AlphabetListDefinition to Choice
renamed AlphabetListChecker -> ChoiceChecker
ChoiceChecker checks the whole input

changes the behaviour of the checker to match the whole input against
any grammar definition of the Choices
Merge branch 'master' into llkrecursive_descent
merged master into llkrecursive_descent
passes lookahead to first_lookup
first tests for PEGParser
refactored mix_result function family