Record Datastore metrics for flatfs and leveldb

Add package comments to packages that are missing them

write memory profiles every 30 seconds when enabled

dont create a new ticker each loop

Currently garbage collection is triggered manually and there are no
age-restrictions on the removal.  I expect we'll eventually follow Git
and auto-launch garbage collection when we hit some threshold of disk
consumption (gc.auto).  I expect we'll also follow Git and keep
unpinned or unreachable objects (gc.pruneexpire, etc.).  But we don't
seem to do either of those yet.

I'm not entirely clear on the role that this package is filling, but
this description seems like a reasonable guess based on a quick skim
through it's exported API.

So folks looking in core can figure out how it fits into the
repository as a whole.

Based on [1].

[1]: https://github.com/ipfs/go-ipfs/issues/1158

Add an OSX LaunchAgent plist

Fix/dial error hiding

`launchd` doesn't allow you to *use* environment variables. Nor does it support
tilde-expansion of program names & arguments after OSX 10.10.

To work around this, I've made the plist file a template and included a small
install script that will interpolate the correct values.

I found this useful to have, and figured it might save somebody else a
few minutes of re-inventing the wheel.

advertise multiple addresses over mdns

use => Use

Eventlog: revert lumberjack fork

Discussion in [1].

[1]: https://github.com/ipfs/go-ipfs/issues/1158

I'm not quite sure which file in this package is the most prominent,
but command.go seemed like a reasonable choice.

Fixes https://github.com/ipfs/ipfs/issues/67

hotfix: dont use nodes context because it might not be set yet

eventlog: buffer writes before pushing them to lumberjack - same effect, no upstream changes. Thx @natefinch!

This reverts commit 7055d769.

Godeps maintenance

use forked lumberjack (buffers writes)

Change ipfs root path volume mount to /data/ipfs

add a benchmark for our hash function

Fix docker $ipfs_data mount path in README