Fix markup stripper tests; don't support \r
Optimize markup stripping regexes
Simplify sentence finder.
Normalize line endings
Simplify and optimize sentence finder
Optimize futher: all decisions in regex now final
Implement new english sentence grader (faster, prefers longer sentences slightly)

--HG--
extra : amend_source : 76fe05b8dc8ebc7eb4d216aeb5a7091f39a6779b