Made checkers variadic
Added new checkers for checking with precision and unary predicates
Make the code look a little better
allow for the zero-arg case

Signed-off-by: Benjamin Teuber <bsteuber@gmail.com>
Add a few zero-arg checkers
Introduce (is ..) as alias for (expect ..) for lazy people
Unit tests for the new checkers
Merge pull request #1 from contentjon/feature/variadic

Feature/variadic