rubylint job templates

Ruby has two versions under Precise: 1.8 and 1.9.3 and they can have
some differences.  The ruby-lint macro thus ruby-lint macro thus accept
an 'interpreter' parameter which must be used to specify the ruby
command to use.

Change-Id: Ib714ad9d7242d0c19bc1a24af11f0e5bdbb7eb51