Separate CallSpec tests by scope.

[serj-lotutovici]

Currently the CallSpecTest is a mess of tests with deferent scopes. Would be nice to separate the tests. For example like so:

• CallSpecBuilderTest - should contain everything related to the builder api
• CallSpecTest - should contain everything related to the CallSpec api (exept for it's reactive apis)
• CallSpecRxTest - should contain everything related to CallSpec's reactive apis.