Add Condition like in assertj-core

[regis1512]

Add a system of condition like in assertj-core : http://joel-costigliola.github.io/assertj/assertj-core-conditions.html

[victornoel]

This would be really useful, for example to test the result of applying a function to a value (for example hashed password comparison).

[VanRoy]

Implemented in release 1.3.0