updated dependencies on bot_io and hop
Generate dependency on latest google_oauth2_client library

Also updated generated hop dependency to >=0.24.0
Move shared client library to top level

Closes #71

Also tightened up the CORS library writer code a bit
generator: some types and tweaks
validating lib generated via CLI
random extra args should throw
must explicitly provide an output directory
DRY'd up some of the tmp dir logic
test: better validating of generated library
starting roll towards 0.6.9
doing library analysis as part of test
hop test now handles generating a lib and analyzing it
fixed help generation, readme output, and spelling of 'version'
moving some shared logic into new tool lib

Better output on 'pub install' fail
bin/generate: removed superflous imports
GenerateResult, fixed some util functions
A bit ugly, but it does analyze all the libraries

Closes #73
bumping dependency versions