Dockerize oplog-dump as worker

This change adds a dockerfile to run oplog-dump as a worker. It does
this by using the baseworker-go/taskwrapper code. This listens to
Gearman for requests to process the job.

This change also publishes the docker image to docker hub.
Merge pull request #3 from Clever/dockerize

Dockerize oplog-dump as worker
Add mongo
Merge branch 'master' of github.com:Clever/oplog-dump into dockerize
Merge pull request #4 from Clever/dockerize

Add mongo
Add retry support to the oplog dump

This is useful because s3 ocassionally fails.
Merge pull request #5 from Clever/add-retry

Add retry support to the oplog dump
Use gearcmd

It has the latest version of the code
Merge pull request #6 from Clever/use-gearcmd

Use gearcmd
Update run as worker to pass SIGTERM correctly to subprocess

The reason we weren't gracefully shutting down before is that bash
won't forward SIGTERMs to processes that are running in the foreground.
Merge branch 'master' of github.com:Clever/oplog-dump into use-gearcmd

Conflicts:
	run_as_worker.sh
Merge pull request #7 from Clever/use-gearcmd

Update run as worker to pass SIGTERM correctly to subprocess
Fix explanation of sigterm handling in bash

Based on my current best understanding of the issue.
Merge pull request #8 from Clever/fix-explanation-of-sigterm-handling

Fix explanation of sigterm handling in bash
Fix race condition in test

Before this change we would do the following.
1. Get the time
2. Sleep two seconds
3. Insert into the database
4. Do other un-related stuff which included inserting one element into
the database
5. Check that if we looked for oplog entries 3 seconds after the time we
got in step1 we would only find the db entry from step4.

This doesn't always work because sometimes rounding meant that the entry we
inserted into the database in step3 was marked as three seconds after
the start time from step1. This meant we would randomly fail this test.

To solve this we now just sleep one second in step2 so that there's no
reasonable way that we could insert the db entry at the wrong time.
Update gearcmd version

This gives us improved logging.
Merge pull request #10 from Clever/update-gearcmd

Update gearcmd version
Merge pull request #9 from Clever/fix-test-race

Fix race condition in test
Merge branch 'master' into filter-by-collection

Conflicts:
	cmd/oplog-dump/oplogdump.go
	cmd/oplog-dump/oplogdump_test.go