Update README.mkd (git:// to https://)

[rakuna]

Original line errors out.
git clone git://github.com/altercation/vim-colors-solarized.git
Cloning into 'vim-colors-solarized'...
fatal: unable to connect to github.com:
github.com[0: 20.248.137.48]: errno=Operation timed out

Proposed line works as expected.
git clone https://github.com/altercation/vim-colors-solarized.git
Cloning into 'vim-colors-solarized'...
remote: Enumerating objects: 336, done.
remote: Total 336 (delta 0), reused 0 (delta 0), pack-reused 336
Receiving objects: 100% (336/336), 151.84 KiB | 765.00 KiB/s, done.
Resolving deltas: 100% (90/90), done.

[jwakely]

Since Vim 8 you don't need pathogen either, you can just do:

mkdir -p ~/.vim/pack/altercation/start
cd ~/.vim/pack/altercation/start
git clone https://github.com/altercation/vim-colors-solarized.git