package: pin `request` to a version that works on node v0.6

This is probably only temporary until v0.6 support is completely dropped,
but I can't foresee that happening until the Ubuntu PPA moves away from
node v0.6 as the default version it installs.

Hopefully this fixes #250 and won't cause other problems. :D
downgrade "request" to v2.12.0

Part of #250.
v0.9.6