added a check on unique key in testImportWithCustomMapperAndAnEmptyInputValue
Revert "number formatter for mapper and foreignKey case fixed to soothe my ocdd"

This reverts commit 18becd0fcaa8bd2b02909ca89db064718294cfcd.
merged TJ's addition of numberFormatter - needs tests
wrestling with git and TJ's reverts
silly merge errors
fixed header from git merge back and forth
fixed more merge errors and added DISPATCH_ONCE for default formatters in place of checking for null
removed default number formatter from default mapper to avoid changing NSNumbers to NSStrings unintentionally
Merge pull request #15 from seanwolter/master

TJ's addition of number formatter and bug fixes and more tests
More helpful log message.
now with better formatting.
Added fetch limit initializer, a #ifndef DLog, and converted NSLogs to DLog. Also added a dealloc method to VIFetchResultsDataSource that conditionally removes delegate/datasource on dealloc if they're equal to the datasource being deallocated (Fixes crashes when datasource is dealloc'd while scrolling.