The main goal of this milestone is to be a workable solution to resolve commone dependency scenarios:

• install from scratch (i.e. empty installed set) bokeh, ipython and iris, an arbitrary list of non trivial packages as far as dependencies go
• for the set of above requirements, we should also have scenarios for updating/downgrading them from a given state of installed package (e.g. an old version of bokeh -> upgrade numpy, or an new version of bokeh, downgrade to an old numpy)
• make sure resolution is reasonably fast (~2-3 sec on a 3 year old laptop)

Out of scope: solving cases where the requested problem is unsatisfiable.