use [[bin]] instead of [[executable]]
auto merge of #122 : Benny1992/cargo/master, r=alexcrichton

Tried with [[executable]] and got this:

```bash
FizzBuzz (master*) $ cargo build                                                                                                             mri-2.1.2
unused manifest key: executable.name
unused manifest key: executable.path
       Fresh fizzbuzz v0.0.1 (file:/home/benny/Web/RustApplications/FizzBuzz)
```

I think ```executable``` section should be ```bin```
Canonicalize github urls for the resolver

In addition to canonicalizing checkout locations, this canonicalizes packages
for the resolver. This allows two dependencies with slightly different urls
pointing to the same repository to resolve to the same location and package.

Closes #104
auto merge of #123 : alexcrichton/cargo/canonicalize-github-urls, r=wycats

In addition to canonicalizing checkout locations, this canonicalizes packages
for the resolver. This allows two dependencies with slightly different urls
pointing to the same repository to resolve to the same location and package.

Closes #104