reset gemset name when loading multiple .ruby-version, fix #2873
silence unexporting nonexisting functions
move __rvm_after_cd to chpwd_functions
use __rvm_run_wrapper instead of calling rvm in migration of ruby, update #2808
bump the gem-wrappers version, update #2838
continuing switching 1.9.2 and 1.8.7 to head for securrity updates
use the same java requiremnts for debina jruby source and binary installation, udate #2871