Update podspecs
Rename classes for RZImport being renamed
Merge pull request #6 from Raizlabs/feature/ndonald2/import-rename

Renaming for change to RZImport
Move subclassable default stack method out of extension category
Also move primary key out of extension category
Add assertions that methods not providing context are called on main thread
Merge pull request #7 from Raizlabs/feature/ndonald2/main-thread-validation

Assert that methods are called on main thread when necessary
Start of README draft
Installation instructions
Fix podspec typo
update installation instructions