Fix path to toggleqvitter.js

Plugin::path() needs its argument to actually be a file that exists
relative to the plugin base directory so that it can determine
whether the plugin is rooted in / or /local.

So don't include HTTP GET args in the path() argument--append them after
getting the value back from path().
Use the background-image even in condensed view.

Scale and position it so as to smoothly transition across the condensed/full threshold.
Prevent background-image from tiling.

Some browsers apparently mess up rendering unless we do this
(discovered in Epiphany on Debian 7.7/wheezy).
Merge pull request #28 from rozzin/bugfixes

Fix path to toggleqvitter.js; CSS background-image fixup.