Bump VERSION to 0.20.3
Merge branch 'release/0.20.3' into development
Bump version forward for development to 0.20.4-dev
Simplify test execution by leveraging `buildImplicitDependencies=YES` (requires xctool >= 0.1.6)
Install xctool directly from unmerged 0.1.7 formula since --HEAD is broken
Uninstall previous version of xctool before installing 0.1.7
Bump AFNetworking submodule reference to 1.3.1
Pass the default `NSURLCredential` through from the underlying `AFHTTPClient` to the HTTP operations that underly object request operations. refs #1480
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
Fix issues with request descriptor matching and add battery of explicit tests for descriptor precedence lookup. closes #1513