Update thumbor-worker Upstart job

Removed enabled=1 check, as you can just use `update-rc.d enable|disable` for that purpose (or add `exit 0` to the default file). Changed instance variable to be more meaningful. Removed bad usage of /tmp (it was unsafe and allowed escalation to root).
Updated thumbor upstart job

Removed check of enabled=1 (see previous commit), renamed port var to ports, adjusted start/stop events slightly.
Changed port to PORT, since default files will override the variable
ports went back to port, so default files do not break
Add http loader configuration keys for cacerts and client ssl
Trying to use .gifv hipster format
gifv support, but still need tests
Gifv content-type testing
running apt tasks on before_script
installing ffmpeg from source
getting out of ffmpeg folder
Merge pull request #379 from renaudguerin/master

Also convert 'LA' mode pictures to RGB before saving to JPEG
Merge pull request #356 from cheister/master

Add http loader configuration keys for cacerts and client ssl
Merge pull request #349 from CameronNemo/master

Update Upstart jobs
Update thumbor-worker Upstart job

Removed enabled=1 check, as you can just use `update-rc.d enable|disable` for that purpose (or add `exit 0` to the default file). Changed instance variable to be more meaningful. Removed bad usage of /tmp (it was unsafe and allowed escalation to root).
Updated thumbor upstart job

Removed check of enabled=1 (see previous commit), renamed port var to ports, adjusted start/stop events slightly.
Changed port to PORT, since default files will override the variable
ports went back to port, so default files do not break
Add http loader configuration keys for cacerts and client ssl
CONTRIBUTING.md: Rename from CONTRIBUTING

Currently, GitHub renders the page as raw text.

[1]: https://github.com/thumbor/thumbor/blob/master/CONTRIBUTING