Test: update Specta, Expecta, and OCMock

[jmoody]

Motivation

I was running some tests on Friday afternoon and discovered that Specta was breaking.

Updated Carthage to use my fork:

• ExampleGroups: do not create shared example groups in initialize #226

We don't use example groups so this fix will work for us.

[jmoody]

@polyakrecords

We use Carthage to manage 3 testing frameworks:

• Specta: rspec style block-based tests for Objective-C
• Expecta: rspec style expectations
• OCMock: mock objects

[jmoody]

@polyakrecords When you get a chance, please review. There is not much here. I just want you to see that we have these three XCTest dependencies.