bugfix for iedit-hide-unmatched-lines

fixed bug where iedit-hide-unmatched-lines goes
into an infinite loop if two matching lines are
exactly context-lines apart
tweak to use isearch case sensitivity

have iedit-mode use the same case sensitivity as isearch if we enter the mode from a search.
also a partial bugfix for when the search has no results
bugfix for when there are no occurrences
Add test case for iedit-hide-unmatched-lines
Merge branch 'master' of https://github.com/mbneedham/iedit
Fix the testcase for iedit-hide-unmatched-lines