Added 3d aliased lines example
Merge branch 'master' of https://github.com/vispy/vispy

* 'master' of https://github.com/vispy/vispy:
  Added EmitterGroup tests Minor bugfixes in EmitterGroup
  Added event emitter tests Minor cleanups / fixes in EventEmitter
  All backends now also emit the close event.
  Wrote more tests for the backends. Also a bit of cleaning.
  Making backends more consistent. A canvas starts out hidden for all backends. Resolved weird viewport offset bug with the pyglet backend.