Use GL 3.2 to illustrate multiple glow package use.

Using GL 4.4 is misleading because the example asks for a version-3.3
context which may not contain future-version functions. In general this
is a tricky combination to get right in production code but this example
simply demonstrates it is possible to initialize two glow packages in
the same program.
Merge pull request #37 from errcw/master

Use GL 3.2 to illustrate multiple glow package use.