Test that basic installer loads el-get immediately

Closes #1457
el-get-issue-407.el: skip emacswiki install

It's not relevant to what we're testing for there, and it takes quite a
long time.
el-get-issue-407.el: remove el-get-notify hack

It's only to support the now-obsolete "stable" version; test-setup.el
already sets el-get-notify-type to 'message.