send search.caseInsensitive to the server to make it possible to do case-insensitve searching
implement case-[in]sensitive searching on the server side (#400)

grep2() was invented to deal with these situations:

1. case-insensitive and fixed matching
2. when the regex is incomplete
update news to reflect changes in DataTables
Merge pull request #579 from yihui/feature/DT-caseInsensitive

Case insensitive searching in DataTables