- added string assertions: contains, contains-not, starts-with, starts-not-with, ends-with, ends-not-with
- added support for IReadOnlyCollection
- added comparable assertions: is-bigger-than, is-in-range
- added support for nullable integers and nullable booleans
- added enumerable assertion has-count
- added support for timespans
- added common asserton is-instance-of
- added string assertions: is-not-empty, has-length