Fix buster-sinon and buster-test dependency versions

I tried installing buster-node 0.1.0 and it failed due to buster-sinon ~0.1 and buster-test ~0.6 dependencies which don't exist in npm registry.
I replaced them with buster-sinon ~0.6 and buster-test ~0.6 instead.

npm ERR! Error: No compatible version found: buster-sinon@'>=0.1.0- <0.2.0-'
npm ERR! Valid install targets:
npm ERR! ["0.5.0","0.5.1","0.6.0"]