Don't log potentially personally identifiable information at Error/Warning/Info levels

I've demoted possible PII to debug logging level. This includes things like
full response strings, key/value pairs of mapping data, etc, since this could
contain sensitive data. My assumption in doing this is that apps should be
able to ship with their logging levels set to Info, and not risk sending any
sensitive data to any 3rd parties that collect app logging, such as Crashlytics.
fix a typo
Merge pull request #2016 from mouse4d/fix/typo-fix

fix a typo in README file
Merge pull request #2014 from sadlerjw/reduce-sensitive-logging

Don't log potentially sensitive information at Error/Warning/Info log levels
Drop bind on Bundler in Gemfile
Convert project to XCTest
Fix NSManagedObject thread violations. refs #2022
Update project to Xcode 6 recommended settings
added missing bracket
Merge pull request #2038 from Kurry/bugfix/1984-typo-in-documentation

added missing bracket in documentation fixes #1984
updated cocoapods gem to 0.34.4
Merge pull request #2052 from Kurry/feature/upgrade-cocoapods

updated cocoapods gem to 0.34.4
Update project format from the old XML using Xcode 6.1

Xcode 6.x will modify the format of the project files, so unless we update its format all new pull request will have conflicts.
Change RKObjectMapping's propertyMappings accessor method to simply return the internal array, rather than making a full copy on every access.  Several methods of RKObjectMapping itself call it like a regular accessor (to get the count, for example) and it gets called a tremendous number of times during mapping operations.  This saves a lot of memory during those operations, plus alloc/dealloc/retain/release/autorelease overhead.
Revert two unintended changes in the last commit

This reverts commit 54cbc9e4130382537eea95f78c24f084031adb07.
Speed up RKDictionaryByMergingDictionaryWithDictionary a bit.  Primarily by avoiding an extra copy of the dictionary at the end, but also don't use -enumerate (has a nested autorelease pool), and use NSDictionary methods and not KV.
Minor performance improvement; check first to see if it's a special key at all before the series of hasPrefix calls, since most of the time it will not be a special key.  The CFStringHasPrefix function did show up as a minor hotspot, and this helps a tiny bit.
Change RKObjectMapping propertyMappings property to be immutable, to avoid having accessor be expensive (pay more of a price during setup instead, instead of the hot mapping code).
Whoops, fix things for the "self" key.  And check for empty keys, though those are illegal with KV on regular objects -- could be OK for dictionaries.
Revert change to RKObjectMapping metadata property.  This loses some of the performance gain (as each sub-operation will now make a copy) but it's less prounounced on a device.