Remove the need to enter an invite code
add correct classes for object attaching on org page

add posts and memberships classes to the lists that contain these in
order allow the ids of the related objects to be correctly attached.
Without this the edit button doesn't act on the model and you end up
creating a new model and the delete button doesn't do anything

Part of #406
call destroy directly on posts model for deleting

Becuase posts are a separate model and not nested within the
organization we need to destroy them directly rather than removing them
from the nested collection and then rely on that cascading the save up
to the organization model. If we don't do this then no API call is made
and the post isn't deleted on the server.

Fixes #406
Fix confusing white space in membership-new.js

bad indenting makes some of the code look like it's part of a block that
doesn't exist
don't set post on organisation if we've not selected one

If we set the post and one hasn't been selected then we end up with the
UI saying undefined where the post should be when we save it as we have
an empty object so the if ( post_id ) check passed but then it has no
properties

Fixes #448
Avoid displaying undefined in post select of membership dialog

If there isn't a post associated with a membership then don't try and
assign and fetch it when creating the memberships dialog. If you do then
it fetches and assigns all posts and then the code to select the
membership for the dropdown gets confused and displays nonsense.
fix jshint tests
Don't run browser based tests by default
Remove documentation from popit repository

This now lives in the https://github.com/mysociety/popit.poplus.org repo
Change docs app to redirect to new documentation

Instead of rendering markdown we simply redirect to the new
documentation on popit.poplus.org
Remove old docs app dependencies that aren't needed
Update info app to redirect to popit.poplus.org
Update links to point to popit.poplus.org
Remove info pages that now reside in popit.poplus.org repo
Remove info pages browser tests