* Support package resolution and filepaths
This change introduces the logic to resolve packages using gotool
and build packages from filepaths. It assumes that the packages
being scanned are located within the GOPATH.
If the GOPATH environment variable is not set the GOPATH is derived
as $HOME/go.
Relates to #184
* Fix build error
* Address unhandled error
* Fix formatting error
* Handle multiple paths on GOPATH
- Get rid of 'core' and move CLI to cmd/gas directory
- Migrate (most) tests to use Ginkgo and testutils framework
- GAS now expects package to reside in $GOPATH
- GAS now can resolve dependencies for better type checking (if package
on GOPATH)
- Simplified public API
