add contains_ignoring_case() string assertion #37
Description
Currently, we have is_equal_to(), is_equal_to_ignoring_case(), and contains():
assert_that('foo').is_equal_to('foo')
assert_that('foo').is_equal_to_ignoring_case('FOO')
assert_that('foo').contains('f')
assert_that('foo').contains('f','oo')Add contains_ignoring_case() for better string assertions:
assert_that('foo').contains_ignoring_case('F')
assert_that('foo').contains('F','OO')