2336: filter tasks properly when building language lists
2344: hack get_subtitle_version to exclude sources

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2337: check for empty language list properly
some additional tests for joining teams and invites
Merge pull request #160 from jdragojevic/wd-invites

some additional tests for joining teams and invites
Merge branch 'i-2337' into staging
Merge branch 'i-2336' into staging
Pinning python-memcached to the previous version (through a specific github commit) cause the latest pypy package is broken, and the maintainers *delete* the old packages.
Fixed lingering line on requirements.txt
Merge branch 'i-2344' into staging