Improved algorithm for stripping spurious <nowiki/> around quotes

* Handles '<i>foo</i> as well as <i>foo'</i> wrt to stripping
  spurious <nowiki/>s

* Removed some <nowiki/> specific tests since those are no longer
  needed.

* Added new test.

* Split an existing test into php / parsoid sections to eliminate
  spurious failures (TODO: There are more probably, but left for
  future patches).

Co-authors: C.Scott Ananian and S.Subramanya Sastry
Change-Id: I8f5adf2bc7a5947f9e735536376e37e1b18df287
Merge "Improved algorithm for stripping spurious <nowiki/> around quotes"