first commit of exercise 49
added concept of sentence equality. got 1st test working
I have no idea what change I made to this test last. -EK
added more parser test cases
made parser more error tolerant by having it simply skip 'error' tuples.
ex49ec3: improved grammar to accept numbers
Merge branch 'master' of https://github.com/frameworkdartboard/LPTHW2ndED