Format the depencies in mix.exp without the additional square brackets

The package pages on expm show the mix dependency as

    {:amnesia,"0.0.1",[github: "meh/amnesia", tag: "v0.0.1"]}

I've been writing about managing projects in Elixir, and I recommended folks copy and paste these lines into their mix.exs files. When José reviewed it, he suggested that it would be better without the [ and ]

    {:amnesia,"0.0.1", github: "meh/amnesia", tag: "v0.0.1"}

I've put together a change for this. It's a little ugly—I suspect there's a smarter way of doing it—but I though you might want to consider it.

Cheers


Dave