Develop new API

[bowsersenior]

2 issues should be addressed:

1. Need a mechanism to create a test case (currently using a lambda) so that test results can be collected and individual tests can be run
2. Allow stubs to be created without using a block. Blocks were a cheap way of safely restoring pre-stub values. The test group mechanism can keep track of stubs and de-stub when it exits.

Something along the following lines:

test_group do
  stub(Object, :method => :foo, :return => 'bar')

  assert Object.foo, :== => 'bar'
end