allow jpi to work on systems with bundler 1.2.

this change is to allow jpi to run on systems which
have bundler >=1.1 and <2.0.

before this change, trying to run jpi on a system with
bundler 1.2 installed resulted in a Gem::LoadError.
Merge remote-tracking branch 'upstream/master' into bundler_12
revert version bump in previous commit.
Merge pull request #59 from echohead/bundler_12

allow jpi to work on systems with bundler 1.2.