Rough and simplistic etcd client.
Rename EtcdClientImpl::ConnMap to ConnectionMap.

Somehow missed this comment in my previous pull request.
Merge branch 'master' into super_duper
Add a comment to the HttpHandler constructor.
Update a few comments in ct-server.cc.

It's true that the SignMerkleTree function would call LogLookup<>::Update,
but that's not the real reason we need to call it at startup. LogLookup
loaded whatever was in the database in its constructor already, the real
problem is when there's nothing at all in the database, we'd serve an invalid
(unsigned) empty STH.
Remove a spurious log message.

The SignMerkleTree already reports the same information.
Log new STHs being served from LogLookup.

This is to be certain that we log this event, no matter what called/caused
it.
Sync up the two implementation of Database<>::LatestTreeHead.

Also use the CHECK family of macros instead of assert(), to make sure they
are always active (if one of these things aren't true, something is very,
very wrong!).
Strengthen a few things in LogLookup<>.
Remove unused methods of Database<>.

Also make two internal methods protected.
Add friendly helper methods to etcd client.
Ignore gmock rather than gtest.
Merge branch 'master' into super_duper

Conflicts:
	cpp/util/json_wrapper.h
Update LogLookup<> through a callback on Database<>.
Add util::Status
comments
Merge pull request #191 from AlCutter/status

Add util::Status and util::StatusOr
Make etcd client use util::Status
200 is ok too!
Merge pull request #195 from AlCutter/etcd_200

200 is ok too!