* Allow no_* to be used for every tests in condition DSL:
condition { no_has_env :shell, '/bin/sh' };
* Modify Test constructor to accept negated: named argument, implement
#negated? and #pass?;
* Rename #success? to #verify in all test classes.
In Condition:
* Modify constructor to accepts tests and a default return value;
* Implement #met?;
* Modify #! so that it return the negated value returned by #met?.
In Condition::DSL:
* Modify .evaluate to build the condition with tests and the value
returned by a the evaluated condition block.
Add a basic Test base class, with env and arguments as attributes.
Add some spec helpers to build some easily testable kind of Test
instances (as test doubles).
