maint: watchr should respect personal account-wide defaults.

Previously the rspec.opts file would override any other options configured for
rspec and, by virtue of being on the command-line, would win against
configuration files.

Now, where a user configuration file exists in ~/.rspec we ignore the shipped
set of options. This allows advanced users to customize without using the
default (and relatively nasty) default rpsec UI.

Reviewed-By: Matt Robinson <matt@puppetlabs.com>