Support escape: true only in ruby_exe, by executing from a temporary file
Support escape: true only in ruby_exe, by executing from a temporary file

* It was never used for ruby_cmd.
* Escaping with the shell is very tricky to do reliably.
* Fixes #11.

ruby/mspec,ruby/mspec,kachick/mspec,kachick/mspec,eregon/mspec