Install via curl should have option "-L"

[Yosuke Akatsuka]

Hello!

README.md introduces the way to install gometalinter via curl command and executing script, I think it needs "-L" option.

• now
  curl https://git.io/vp6lP | sh

• should be
  curl -L https://git.io/vp6lP | sh

It seems the URL returns 302 as response code, and the response includes alternate location of the script. With "-L" option, curl automatically tries to get from alternate location. I confirmed downloading gometalinter via curl with "-L" option works well.

[Yosuke Akatsuka]

@alecthomas
Hi! I just submitted a pull request for this issue. :)
I'm happy if you check it. Thanks!

[Alec Thomas]

Thanks!