added install_options to gem provider.  no you can do... install_options => [ '--config-file=/root/.gemrc' ]
Merge remote-tracking branch 'mmoghadas/adding_install_options_to_gem_provider' into PUP-620-add_gem_install_options
(PUP-620) `install_options` only for Install 

The previous implementation would use the install options for commands like `list` which would cause errors. This makes sure that only the install option uses `install_options`