Sort PackagesList by name and version
In PackageList, sort the package version from latest to oldest

This enables us to return the latest version of a package when no version is specified rather than the oldest.
Therefore, we don't need to modify the search algorithm to return the latest version of a package.
Merge branch 'deterministic_package_search' of https://github.com/simonaquino/aptly into simonaquino-deterministic_package_search
Add Simon Aquino to authors. #67
Enable system tests fixture under go1.3 as well. #72
Simplify Makefile.
Insert into right position when adding as well. #67
Merge branch 'simonaquino-deterministic_package_search'