Invitation link to an event

[sirex]

Send invitations, when event is created. Invitation should be sent only to all participants of parent event.

For now, no html mails and only one link.

Depends on: #21, #22, #25.

[sirex]

https://cucumber.io/ - can be used for testing.

To write tests you have to:

1. Define some fixtures using factory boy factories (pylab.core.factories).
2. Call a unit.
3. Check if right amount of emails was sent.