Fix Widget#render docs

* Fix broken link
* Method just calls super, so (not full now) list of options is needless
Merge pull request #92 from kuraga/patch1

Fix Widget#render docs
fixing test.
remove 1.8 CI.
run CI against rails 3.0-4.0. fixes #86.
removing Gemfile.lock files.
make most tests work. switch over to minitest.
use a regex for testing assertion message.