Remove minitest warnings on ruby 1.9.3
Move Tunit::Spec::DSL to a file of it's own
Define `expect` in Tunit::Spec

For it to only be accessible in the spec DSL
Wrap given value as a proc to defer calculation
Add `to` and `not_to` to calculate the values
Add expect dsl

In the way of expecting a value to equal or not to equal another
Add error handling for faulty assertions
Dynamically define matchers depending from assertions

Raise hell if not assertion can't be found
Expectations must be inside an it block
Move expectations to mixin
Execute assertions from the caller class
Set assertions in test klass to avoid empty test errors
Split up method_missing test

* positive assertions
* negative assertions (refutions)
* that it only maps methods to the cases above