Merge tag '0.2.5' into develop

0.2.5 (2017-12-15)
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Features:

- Import: can now specify search template when querying import sources (#45)
- Login form: now redirect to previous page after login (#2)
- 404: a decent 404 template, at least (#48)

Bugfixes:

- Player: better handling of errors when fetching the audio file (#46)
- Csrf: default CSRF_TRUSTED_ORIGINS to ALLOWED_HOSTS to avoid Csrf issues on admin (#49)

Tech:

- Django 2 compatibility, lot of packages upgrades (#47)