Update README: use jekyll serve subcommand to avoid deprecation error

$ jekyll --serve
       Deprecation: Jekyll now uses subcommands instead of just switches. Run `jekyll help' to find out more.
invalid option: --serve
Merge pull request #2 from liliakai/jekyll-error

Update README: use `jekyll serve` subcommand to avoid deprecation error
Add Gemfile and Makefile FREEBIE
Merge pull request #10 from kyleconroy/makefile

Add Gemfile and Makefile