Ensure that Foundation.framework is imported before checking `NS_BLOCKS_AVAILABLE`

Fixes #786
Fix logging levels
Update save documentation with specific notes about MR_contextForCurrentThread
Remove swizzled approach to importing with -valueForUndefinedKey:
Catch an expected undefined key exception when importing
Remove unnecessary "isImporting" property
Remove unnecessarily public method from interface
Latest Expecta
Move the import controls into a formal protocol
Use proper bundle format for XCTest bundles
Klass just sounded a bit wrong…
Bump podspec to 2.3.0-beta.3
Developer can define MR_LOGGING_CONTEXT to log MagicalRecord entries in specific context in  Lumberjack.
Added missing import to MagicalRecordShorthand.h.
Changed occurences of MR_DEPRECATED_WILL_BE_REMOVED_IN_3_0 to MR_DEPRECATED_WILL_BE_REMOVED_IN("3.0")
Merge pull request #830 from CraigSiemens/feature/shorthand-build-failure

Fix shorthand imports, and deprecation macros
Merge pull request #827 from jozefizso/feature_mr_logging_context

Add MR_LOGGING_CONTEXT to allow the developer to set a Cocoa Lumberjack context when logging (defaults to 0)
Perform MR_workingName activity on the context's queue