Refactor

[fubarhouse]

So, it has been forever since I've really looked at DVM.

Maybe it's time I give it some love based on experience elsewhere.

Priorities:

• Remove calls to exec.Command{} where possible.
• exec.Command calls should not use environment-specific formatting (Should help with #102)
• Cut down excessive parsing
• Cut down excessive logic
• Break composer/drush command calls into independent packages
• Segment composer and legacy versions better
• Fix and identify installed version better
• Speed enhancements (such as caching for legacy versions)