Put the account to use in the url instead of the session. In this way we
can use many accounts in many tabs.
Display correclty the error message
Use self._response
Fix tests
Raise IOError if a directory doesn't exist
catch exception when the directory doesn't exist
Validate the extension of the filename
Add explore function and be able to pass a file to edit directly
Always use 'path' in the query strings
Be able to edit file as text.
We can have an error message with a content to display