remove 1.8.7 support from README
Merge pull request #2227 from opscode/lcg/ruby193docfi

remove 1.8.7 support from README
remove chef/shell_out dep

seems like we can drop this require for chef-12
Revert "remove chef/shell_out dep"

This reverts commit c62f97362b94aa13d2c7cbf77641c8c10a6e69dc.

derp.