tests(sharness) attempt to execute sharness tests on ipfs2

@jbenet @chriscool

(not to be merged into master) This is a hack to run sharness tests on
th ipfs2 binary. Instead of compiling cmd/ipfs, it compiles cmd/ipfs2
and copies this into test/bin/ipfs.

I thought this would be enough to pass the `basic-commands` test, but
it's not.

Although the output is fairly similar, the `ipfs version` test fails.

```
test (feat/test2) λ. diff version1 version2
1c1
< ipfs version 0.1.7
---
> ipfs version 0.1.5
```

I'm not very experienced with `sh` scripting, so perhaps I'm missing a
key ingredient or maybe misunderstanding the the tests are meant to
work.

Would like to get input on this.

Thanks, @maybebtc

test/Makefile

@@ -32,8 +32,8 @@ $(SHARNESS):
 ipfs:
 	@echo "*** installing $@ ***"
 	mkdir -p bin
-	cd ../cmd/ipfs && go build
-	cp ../cmd/ipfs/ipfs bin/ipfs
+	cd ../cmd/ipfs2 && go build
+	cp ../cmd/ipfs2/ipfs2 bin/ipfs
 
 random:
 	@echo "*** installing $@ ***"