Remove gitter from README [ci skip].
Remove gitter from README [ci skip].

ruby-bench/ruby-bench-web,treble37/ruby-bench-web,klgilbert/ruby-bench-web,treble37/ruby-bench-web,treble37/ruby-bench-web,bmarkons/ruby-bench-web,klgilbert/ruby-bench-web,bmarkons/ruby-bench-web,klgilbert/ruby-bench-web,bmarkons/ruby-bench-web,tgxworld/ruby-bench-web,tgxworld/ruby-bench-web,ruby-bench/ruby-bench-web,tgxworld/ruby-bench-web,ruby-bench/ruby-bench-web