Changed Release.Dependencies to be []*Package

Signed-off-by: Phan Le <ple@pivotallabs.com>
Changing Job.Packages to Job.PackageNames

Signed-off-by: Phan Le <ple@pivotallabs.com>
Working implemetation of Release.Dependencies

* using Topological Sort algo
* using *Package and []*Package
Signed-off-by: Phan Le <ple@pivotallabs.com>
Refactored pointers into dependencyAnalysis

Signed-off-by: Phan Le <ple@pivotallabs.com>