Bugfix release for 0.9:

* pin to the newest psych gem
* remove better_errors gem
* fix login error message with non en locales

Features:

* destroy invites used to create test accounts
* sort invite codes by last update

feat: sort invite codes by last update

Closes #8806

See merge request leap/webapp!48

They used to be sorted by the code which was not helpful

fixes #8806
requires deploy of new design docs to the platform

fix: destroy invites used to create test accounts

See merge request leap/webapp!47

Production instances are getting cluttered with invites from
test accounts. Instead of marking them as used we will now completely
remove them.

refers to #8804
refers to #8807\

fix: login error message with locale set

Closes #8805

See merge request leap/webapp!46

On a failed login the warden failure app gets called.
Some of the params are changed accordingly but controller
and action remain.
set_locale would detect there was no locale in the path
and thus attempt to redirect. However the params still
belong to the previous request which was a POST to
  Api::SessionsController.
This route does not respond to get requests and so it
would trigger a 404 in production and a 500 in development.

This commit prevents set_locale to act upon warden failure
app controller calls by adding /new to the list of
`NON_LOCALE_PATHS`. (The path is updated by warden to the
name of the action called in the failure app).

A test is included in this commit that tries to login
with an invalid username, password combination and a german
locale set.

fixes #8805

pin to the newest psych gem, so as to not hit bugs in older versions (required by faker)

See merge request !44

it is currently incompatible with haml