Do not treat apostrophe as a word boundary

In case the word to be fixed has apostrophes, codespell was not making
the right fix. E.g:

i) "doesn't" was read as two separated words: "doesn" and "t"
ii) "doesnt'" was read as "doesnt"
iii) "doens't" was read as two separated words: "doens" and "t"

(i) is not a big deal since the spelling is right. In (ii) the fix would
be obviously wrong, since the net result would be "doesn't'" since the
doesnt->doesn't would apply in this case. (iii) is even worse since the
doens->does rule would apply and the result would be "does't"

Adding apostrophe to the list of chars treated as word boundary (i) and
(iii) are fixed and new rules are added to the dictionary in order to
fix (ii).