Change assert_match parameters order.

Tests suite doesn't pass for ruby 2.0.0-p247 (and for all 2.0.0 rubies I guess).
Minitest::Assertions define assert_match as:
**def assert_match matcher, obj, msg = nil**

Ruby 1.9.x doesn't complain if you switch _matcher_ and _obj_ but ruby 2 does and raise:
**TypeError: no implicit conversion of Regexp into String**