fix broken link (s/ftp/https/)
fix broken link (s/ftp/https/)

Signed-off-by: Jeremiah Mahler <0c597d45353d741b4835ff5e56c2bc263abede5d@gmail.com>

src-d/go-git,src-d/go-git,go-git/go-git,go-git/go-git,mcuadros/go-git,mcuadros/go-git