Find links

All download and unpack calls wrapped into single func. So you can disable certificate, add new archive type support, etc. in one place.

All package archives are searched at url specified using --find-links. Originally they were scattered around library ftp servers, our amazon S3 and github. Now all packages are searched in one (or several) places. By default it is set to http://share.braincorporation.net/robustus/source_packages

Updated pip, wheel, setuptools, because there was problem making wheel for PySide. It took too much time without producing any output and travis stopped the build. For now, PySide test is still disabled, because it takes too much time. But I hope packages that are using it will be able to build it now and upload to travis wheelhouse cache.