handle user navigating quickly

- only the last click is finally considered the intended click.
- if the user clicks too fast, we assume he doesn't want to even store the intermediate locations in the history...
enable cross-domain requests on IE
some error handling
better naming and replacement logic
get ajax settings from initialiization
Merge branch 'master' of https://github.com/darksmo/djax
support blocking callback on djax click
deferred djax