Pin Rake for Ruby 1.8.7

Rake 10.2 has dropped Ruby 1.8.7 support, this patch pins that version to use
10.1.1.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #896 from kbarber/maint/1.5.x/pin-rake-gem

Pin Rake for Ruby 1.8.7