organize imports
privatize getLedger method
substitute with LedgerMap type
hide ledger wantlist manipulation
privatize fields in ledger
fix(bitswap:ledger) race conditions

https://github.com/jbenet/go-ipfs/issues/39
chore(deps:go-multiaddr) update to b90678896b52c

procedure is to execute
```
cd my/github.com/jbenet/go-multiaddr
git pull
cd my/github.com/jbenet/go-ipfs
godep update github.com/jbenet/go-multiaddr
```
Merge pull request #46 from jbenet/deps/go-multiaddr-b90678896b52c3e5a4c8176805c6facc3fe3eb82

chore(deps:go-multiaddr) update to b90678896b52c
Merge pull request #38 from jbenet/feat/bitswap-import-cleanup

chore(bitswap) tidy up bitswap, ledger
config: Broke out config directory into its own const
config: Made WriteConfigFile create config parent directory if it doesn't exist
cmd/init: Fixed init checking if config exists
Merge pull request #49 from mappum/feat/init-fix

Init Fix
core: Refactored node initialization
core: Don't require address for node initialization
core: Show error when config identity is not set
core: Updated basic initialization tests
Merge pull request #1 from jbenet/master

give