Planning, write the planned API in documentation

No implementation yet.
Basic CURD test interfaces
Rename Respond as Response

Respond is a verb. Response is the noun.
Implemented all Expectations planned

Implemented:
1. ExpectResultCount
2. ExpectResultsValid
3. ExpectResultNth
4. ExpectResultToPass

Need unit test for these
Implemented WithResponseAs
Fix issue with "r" in Run

r is a pointer. It's value needs to be allocated before use.
Fixed issue with Case.ExpectResultsValid

ExpectResultsValid should expect no parameter(s). It should loop
through all items instead of just checking the first one. Now fixed.

Also improve the error message if item found invalid.
Added test for an ordinary Create case
Change expectation to use Response

Using the interface directly is better and cleaner than using pointer.
Migrate unit test related struct

Move definiton of dummyResponse and dummy out to response_test.go
More readable
Finish unit test for all expectation related code
Implemented WithParam for Case