fix(bitswap) shut down async
feat(Dockerfile) use ENTRYPOINT

Fixes #258

https://github.com/jbenet/go-ipfs/issues/258
feat(init) display peer id in init command

use case:

Just configured and installed a node.

benefits:

1) reduces friction when setting up a new node

2) reveals useful details about the workings of the system. It's the
user's first encounter with her node's identity. The tour can build on
the user's knowledge.

```
ipfs (maybebtc-november) λ. ipfs init -f
initializing ipfs node at /Users/btc/.go-ipfs
generating key pair
peer identity: QmcRbn41Vc2CvbpLYfN36mAWusErKWvAAHbq92LPra2gFT
```
fix(commands/http/client) cast safely
fix(commands/request) cast safely

should be able to look at a function in isolation and prove it won't
panic. if that's not possible, should cast safely.
fix(peer) update latency
doc(peer)
Merge pull request #267 from jbenet/maybebtc-november

Miscellaneous fixes
probably fix OSX ipns bug
probably fix the cat bug
tests: use shasum instead of sha1sum

sha1sum is not in osx by default.
shasum seems to be everywhere.