supress output from which when searching fo system commands, update #2854
improved code to checkout tags and revisions, update #2854
fix installing jruby version from source, fix #2854
make sure epel is installed only on proper autolibs state, improve messages, fix #2841
clean PATH entries ending with /, fix #2826
fix selecting installed rubies with patches, fix #2857
add chpwd_functions handling for bash and old zsh, fix #2819
do not redefine __zsh_like_cd when already available, update #2819
more precise implementation of chpwd and chpwd_functions from Zsh, update #2819
always define __zsh_like_cd, there is no sense in forbiding an updated version to be loaded, update #2819