Revert "Makefile: Always use ssh access to clone repository"

This reverts commit e0b7a0bf92.

Makefile

@@ -7,8 +7,14 @@ home ?= $(HOME)
 
 dotfiles_url_base := https://raw.githubusercontent.com/10sr/dotfiles/master
 use_git ?= t
+git_auth ?= t
 
+ifneq (,$(git_auth))
 dotfiles_git := git@github.com:10sr/dotfiles.git
+else
+$(warning 'git_auth' is empty. Use public read-only git repository.)
+dotfiles_git := http://github.com/10sr/dotfiles.git
+endif
 
 current_origin_url := $(shell git config remote.origin.url)