(PUP-2913) Update to rgen 0.7.0

This commit matches the changes made to puppet in commit ed5d73424 for
PUP-2831.
(maint) Remove gem docs saving about 5 MB
Merge pull request #49 from joshcooper/ticket/1.9.3-x86/PUP-2913-rgen-0.7.0

(PUP-2913) Upgrade ruby 1.9.3-x86 to rgen 0.7.0