js: wrap CSRF javascript in jQuery(function(){})

Also remove the unnecessary `csrftoken` variable and use the `getCookie`
function directly.
Fix handling of invalid choices in `choices_for_values`

Fixes https://github.com/yourlabs/django-autocomplete-light/issues/62
tox.ini: add {posargs} placeholder to pass arguments easliy
Fixes a bug where ampersand cannot be typed on Chrome/Mac
Merge pull request #306 from aidanlister/patch-1

Fixes a bug where ampersand cannot be typed on Chrome/Mac
Merge pull request #297 from blueyed/ajax-csrf-on-dom-ready

js: wrap CSRF javascript in jQuery(function(){})
Merge pull request #298 from blueyed/fix-issue-62

Fix handling of invalid choices in `choices_for_values`
Merge pull request #304 from blueyed/tox-ini-posargs

tox.ini: add {posargs} placeholder to pass arguments easliy
Use `queryset` from a ModelChoiceField for `choices`

Fixes https://github.com/yourlabs/django-autocomplete-light/issues/300
Sort/cleanup imports