Added properly functioning case insensitive match without regex

pandas.core.strings.str_contains should now match case insensitivity properly if given regex=False and case=False.  Also added test cases for case insensitive pandas.core.strings.str_contains with and without regex.
Documentation for str_contains bug in changelog
Merge branch 'fix_string_contains_case_insensitive_with_no_regex' of https://github.com/benjwadams/pandas into benjwadams-fix_string_contains_case_insensitive_with_no_regex

Conflicts:
	doc/source/v0.14.1.txt