AssertJ support

[asafm]

Hi Richard,

This project looks really useful and cool!
We mainly use AssertJ in our unit tests - I found it to be much more readable than Hamcrest Assert functions.

Have you thought about support this lib as well?

[manikmagar]

I prefer using AssertJ over Hamcrest for the same reason. It will be nice to be able to use AssertJ, similar to Hamcrest.

[glebsts]

Miss that as well.