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]
SpecHelper -> CDRSpecHelper

- SpecHelper.h is retained for compatibility with a deprecation warning,
  as it is likely to be imported at the top of users' spec files.
Don't include Cedar-iOS as a header directory in the Podspec

- This effectively namespaces the Cedar headers, preventing:
`#import "CDRSpecHelper.h`
and instead requiring:
`#import "Cedar-iOS/CDRSpecHelper.h`
Prefix CDRSpec's global currentSpec
Prefix public symbols from CDRFunctions.h, deprecating the original names
Update templates to account for the namespacing changes
Allow returning `nil` from stubs on appropriate methods

[#38236493]
Allow any rake version during install

Stops rvm+bundler integration from complaining about not using the rake
version in the Gemfile. See: http://rvm.io/integration/bundler
Merge pull request #243 from pivotal-brian-croom/improve-namespacing2

Improve namespacing
Merge pull request #234 from pivotal-brian-croom/release-spec-blocks-after-execution

Release spec blocks after execution
Fix issues with spies leaking

- Explicitly stop spying on objects after each example
- No longer relies on the timing of CDRSpyInfo instances being deallocated
- This fixes leaking caused by release messages being lost after the currentSpies__ set is cleared
- Spies now forward the private -retainWeakReference method to their real object which fixes overrelease bugs for objects which use a different reference counting implementation than NSProxy (e.g. some UIKit objects)

[#69580040]
Merge pull request #235

Fix issues with spies leaking
Fixed cedar plugin to avoid [NSThread isMainThread] assertion under a race condition
Merge pull request #245 from pivotal-brian-croom/and_return_nil

Allow returning `nil` from stubs on appropriate methods
Merge pull request #247 from jeffh/plugin-1.1

Fixed cedar plugin
Fixed podspec lint by explicitly setting MRC
Bumped podspec version to 0.9.7