Implement ipfs ping

core: make sure to call swarm.FilterAddrs

also move network setup into its own self-contained func

linkblock size calc test

osxfuse: fix version check

fix ping test

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

Conflicts:
	core/commands/root.go

begin ping command, WIP

finish initial ping implementation

benchmark Sign and Verify operations

BenchmarkSign1B             1000           2406924 ns/op
BenchmarkSign10B            1000           2360527 ns/op
BenchmarkSign100B           1000           2354136 ns/op
BenchmarkSign1000B           500           2361775 ns/op
BenchmarkSign10000B          500           2415993 ns/op
BenchmarkSign100000B         500           2718051 ns/op
BenchmarkVerify1B          30000             52117 ns/op
BenchmarkVerify10B         30000             50968 ns/op
BenchmarkVerify100B        30000             51037 ns/op
BenchmarkVerify1000B       30000             56768 ns/op
BenchmarkVerify10000B      10000            105744 ns/op
BenchmarkVerify100000B      2000            628530 ns/op

install-sharness.sh: use git instead of wget and shasum

License: MIT
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>

path: ignore prefix /ipfs/

gc closed conns

Fix test_docker Makefile target and rename it test_3node

```
2015/01/07 21:57:16 COPY has been deprecated. Please use ADD instead
```

Thanks @inconshreveable