Move completely to go15

[christiangriset]

For context, see https://clever.atlassian.net/browse/INFRA-1112

This PR was autogenerated. @nathanleiby you were chosen as the most active commiter of this repo, please review and check that builds still pass.
Some known, but difficult to automate, errors are:

• In the Makefile and test_drone.sh, performing go get on the repo while it's now only necessary for packages such as errcheck or lint.
• Makefile testing vendored dependencies (which in turn tries to compile them, oftentimes creating import errors).
• Dependencies aren't compatible with go1.5. For example appasaurus ran into this with gopkg.in/mgo.v2 (the solution here is to run go get -u gopkg.in/mgo.v2).

If there are any problems, feel free to ping @cgclever for troubleshooting.

For understanding Godeps and vendoring see this doc.

Thank you!

[nathanleiby]

having issues with dependency on raven-go

# cd .; git --git-dir=/var/cache/drone/src/github.com/getsentry/raven-go/.git submodule update --init --recursive
No submodule mapping found in .gitmodules for path 'docs/_sentryext'
package github.com/getsentry/raven-go: exit status 1
make: *** [github.com/Clever/gearcmd/cmd/gearcmd] Error 1

cc: @cgclever have we resolved this already in other repos?

[christiangriset]

@nathanleiby: tl;dr, needed to add vendored deps.

What happened here was a deficiency of the gitbot script. It wasn't smart enough to know that there were some repos which need vendoring, though they didn't before. This is an example of a repo which ran go get -d -t in the Makefile, so there was never any reference to vendoring (so the script chose not to). This change removed said go get command from the Makefile and added the appropriate vendoring.

[nathanleiby]

thanks for the fix!