Display all error messages for TextWidth

Previously, the `TextWidth` hook would halt early if the subject line
was overlength, and not show errors for the other overlength lines in
the commit message.

Now it collects and displays all error messages.

Change-Id: I2f0e113031a5d28ad89dabaa11388493716354fc
Reviewed-on: http://gerrit.causes.com/35900
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>