Mention Rails 4 support in README.md. [ci skip]
Mention Rails 4 support in README.md.
[ci skip]

sopheak-se/breadcrumbs_on_rails,ngelx/breadcrumbs_on_rails,weppos/breadcrumbs_on_rails,hoahm/breadcrumbs_on_rails,balikcina/breadcrumb,sopheak-se/breadcrumbs_on_rails,comparaonline/breadcrumbs_on_rails,ushahidi/breadcrumbs_on_rails,ipmobiletech/breadcrumbs_on_rails,ushahidi/breadcrumbs_on_rails,victor95pc/breadcrumbs_on_rails,ipmobiletech/breadcrumbs_on_rails,ngelx/breadcrumbs_on_rails,victor95pc/breadcrumbs_on_rails,weppos/breadcrumbs_on_rails,comparaonline/breadcrumbs_on_rails,hoahm/breadcrumbs_on_rails