Support a trim_mode of -
Support a trim_mode of -

This ensures that templates and partials with <%- and -%> will pass
syntax checking.

gnagel/overcommit,TheSooth/overcommit,blech75/overcommit,oxocode/overcommit,oxocode/overcommit,gnagel/overcommit,TheSooth/overcommit,blech75/overcommit