Fix two bugs when filterIgnoreCase is false

1. When fillOnBlur is false, matching that occurs when Enter is pressed
ignores case.
2. Invalid value checks ignore case.

See http://jsfiddle.net/gjsjohnmurray/ntge0beb/
Merge pull request #30 from gjsjohnmurray/#29

Fix issue #29 (two bugs when filterIgnoreCase is false)