Fix pivotal tracker integration removing requested_by attribute

[jpl]

The "requested by" attribute needs to match username in pivotal tracker (which is often not the case, and seems quite buggy on the pivotal side), and is not mandatory as the request is by default owned by the token api submitted during integration.

[TeatroIO]

I've prepared a stage. Click to open.

[coveralls]

Coverage decreased (-0.0%) when pulling bebedda on jpl:master into 514633b on errbit:master.

[stevecrozz-]

I've noticed this too, but just for the sake of argument, wouldn't it be better to just set your errbit usernames equal to your pivotal user names? That would allow you to know who raised which issues rather than having all issues seem to be raised by the same user.

[stevecrozz]

All the issue tracker plugins are in individual repos now. The pivotal plugin currently lives at:
https://github.com/brandedcrate/errbit_pivotal_plugin

If anyone makes a few good contributions and wants to own the repo, I'd be happy to transfer it.