Accept `sfields` to be a comma-separated string of fields

This aligns with the query parameters accepted in the editor and allows
using both comma-separated and multiple parameter forms.

Fixes evernote#46.
Identify 404 errors as such
Add comment to clarify the purpose of some code
pootle_profile: Move profile URLs to /profiles/

/accounts/ is reserved for accounts (authentication) related urls
contributors: If the user does not have a username, treat as anonymous
Docs: bump our documented minimum Django versions

Also try document this in the requirements file and release guidelines
to catch this type of error earlier.
Docs: typo
runner: Fix the input() shim if run from `pootle'
setup.py: Use new-style exception syntax
Cleanups
Cleanup: Move constant inside function

It was not used in any other place, so this makes clearer that can be
removed with no side effects.
Simplified event binding/handling
Simplified some code
Don't poison the global scope
Simplified some selectors
Micro optimizations
Use `on()` rather than `bind()`
Disable submission button if no change has been made

Fixes evernote#67.
Cleanup: removed oldIE-specific declarations
Ugly workaround to avoid submit button jumpiness