Don't require compare_equals for returning values on stub_method

- ReturnValue is no longer a ValueArgument subclass, which brought along unwanted behaviors

[#39969975, #65424036]
Remove spec describing a behavior in a situation that never arises

- It was a false negative anyway. CDRExampleGroup reports a change to its state property any time a child changes state, whether or not the that makes the group's state is actually change
Instances of CDRExample and CDRExampleGroup are only allowed to run once
CDRExample and CDRExampleGroup release their spec blocks once they have finished running

[#66016196]
Fix memory management issues in CDRExampleSpec

I ran into these while running with zombies turned on. It seems the new example instances were always ending up allocated at the same memory address as the one just released, so the earlier autorelease ended up getting applied to the "replacement" example instead of the one it was initially called on
Fix leak in spec
Fix another leak
Fix more leaks
Fix static analyzer issue
contain(an_instance_of(Class))
Support contain(...).as_a_key(), contain(...).as_a_value() for use with dictionaries
Merge branch 'pivotal-brian-croom-contain_an_instance_of'
Copy more headers into the frameworks

Once again master got broken because this was forgotten :(
Improve handling of `nil` values in the equal comparator and when matching method arguments

- Properly match methods invocations which include a `nil` argument [#63351266]
- Fix stringifiers for NSNumber and for generic objects to correctly handle nil values
- Fix the compare_equal matcher for two NSNumber's to not blow up if the expectedValue is nil [#69580148]
- Equal matcher fails explicitly when used with nil
  - In this situation, presumably the value passed in was intended to not be nil, hence it is treated as a failure
  - The be_nil matcher is mentioned in case checking for nil was the actual intention
- be_nil matcher can be used with block values [#42698619]
`rake upgrade` doesn't choke on paths with `~`
Merge pull request #230 from pivotal-brian-croom/stub-return-values-dont-need-comparator-or-stringifier

Stubs can return types that don't have compare_equals or a stringifier
Merge pull request #238 from pivotal-brian-croom/rake-upgrade-expand-path

`rake upgrade` doesn't choke on paths with `~`
Merge pull request #226 from pivotal-brian-croom/fix-invocation-matcher-with-nil-as-id

Improve handling of object-typed nil values during argument matching
Refactor test boot methods

- Common code consolidated into CDROTestRunner and CDROTestIPhoneRunner
- CDROTestIPhoneRunner subclasses CDROTestRunner
Update podspec to not exclude CDROTestRunner on iOS