Unpin beaker now that 1.7.0 is released

We had a pinned version of beaker. This patch unpins it now that the code that
we need has been released.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #873 from kbarber/maint/1.5.x/unpin-beaker

Unpin beaker now that 1.7.0 is released