Merge pull request #52 from laanwj/master

Un-hardcode host/guest IP
Fix issue #56: clean up environment before gbuild'ing

Originally proposed by cfields
Merge pull request #57 from gdm85/master

Fix issue #56: clean up environment before gbuild'ing
Extend gverify comparison

- Allow comparing against a sepcific 'golden' manifest with `--compare-to`
- By default pick the first manifest to compare to, instead of always
  comparing against the previous one, which is confusing
- Show line-by-line difference if `-v` given