Add other installation methods using different package managers

[RohanVB]

As https://github.com/coala/coala-vim/pull/27/files does for vim-plug; we can ultimately choose to keep the entire installation methods or we can list out which package managers support the installation of coala-vim.

[tmmsartor]

In my opinion listing available installation methods will make the plugin look better on the eyes of coala newcomers.