Merge branch 'release/v0.20.0-rc1'
Merge branch 'release/0.20.0'
Drop pre from README.md install instructions
Merge branch 'release/0.20.1'
Adjust version and tag in Podspec for release
Merge branch 'release/0.20.2'
Merge branch 'release/0.20.3'
-[RKPaginator cancel] invalidates objectRequestOperation.
Add support for deleting local objects in response to a 404 (Not Found) or 410 (Gone) status code. closes #1292
Copy state of `allowsInvalidSSLCertificate` and `SSLPinningMode` from the HTTP client to operations constructed by `RKObjectManager` fixes #1454
Fix leaks of `NSBlockOperation` objects in the search indexer. closes #1478
Add tests ensuring that cancelled response mapper operations invoke the `didFInishMappingBlock` and do not result in object request operations being left in an operation queue. fixes #1494
Perform Travis CI build with latest release version of xctool
Execute `brew uninstall` before `brew install` to fix build errors on Travis
Add Support dependency to the ObjectMapping sub spec and migrate logging source files into Support subspec
Switch to rbenv from rvm.

* Remove ruby- prefix in .ruby-version
* Delete .ruby-gemset
Add Bundler config file and bin directory to .gitignore
DRY up version configuration in Podspec
Enables installation of Network and ObjectMapping sub-specs via CocoaPods without requiring Core Data
Add missing conditional compilation to the testing classes for use standalone from Core Data