convert DAGService to an interface

Fix logs + msgio error

Use Sharness as our shell test framework, version 3

You can use it like this to launch all the
test scripts in order:

$ cd test
$ make
 rm -r test-results
 *** t0010-basic-commands.sh ***
 ok 1 - current dir is writable
 ok 2 - ipfs version succeeds
 ok 3 - ipfs version output looks good
 ok 4 - ipfs help succeeds
 ok 5 - ipfs help output looks good
 # passed all 5 test(s)
 1..5
 ./test-aggregate-results.sh
 fixed   0
 success 5
 failed  0
 broken  0
 total   5

Or you can just run one test like this:

$ make t0010-basic-commands.sh
 *** t0010-basic-commands.sh ***
 ok 1 - current dir is writable
 ok 2 - ipfs version succeeds
 ok 3 - ipfs version output looks good
 ok 4 - ipfs help succeeds
 ok 5 - ipfs help output looks good
 # passed all 5 test(s)
 1..5

This script aggregates test results using Sharness.

This way we can easily reuse the checks in
test-sharness-config.sh.

This checks a little bit the installation and some
basic commands.

You can run it like that:

$ cd test
$ ./t0010-basic-commands.sh
 ok 1 - current dir is writable
 ok 2 - ipfs version succeeds
 ok 3 - ipfs version output looks good
 ok 4 - ipfs help succeeds
 ok 5 - ipfs help output looks good
 # passed all 5 test(s)
 1..5

Our test framework is based on Sharness.
So the first thing to do is to source it.

redux: refactor(dht/pb) move proto to pb package

go-vet friendly code

- distinguish log.Error and log.Errorf functions
- Initialize structs with field names
- A bit of unreachable code (defers)

until https://github.com/op/go-logging/pull/30 is merged

fix(bitswap) data races

addresses concurrent access in bitswap session

fixes data race detected in a testnet test

dht fixes

refactor(pb) move protos to internal packages