'Implements Step 5a from "An algorithm for suffix stripping"
From the paper:
Step 5a
(m>1) E     ->                  probate        ->  probat
rate           ->  rate
(m=1 and not *o) E ->           cease          ->  ceas'

def _step5a(self, word):

    if word.endswith(u'e'):
        stem = self._replace_suffix(word, u'e', u'')
        if (self._measure(stem) > 1):
            return stem
        if ((self._measure(stem) == 1) and (not self._ends_cvc(stem))):
            return stem
    return word
