v0.2.0

This release adds some new functionality:

• Inclusion and exclusion constraints (Permitted, Forbidden and Required), specifying which agents an agent can or must receive.
• Leximin allocation, via the alloc_lmm function (where LMM stands for "Lexicographic Maximin").
• Proper handling of asymmetric constraints (i.e., ones that apply differently to different agents) in MMS-allocations, along with the possibility of supplying separate options for the mms function when calling alloc_mms, through the mms_kwds argument.
• Initial, basic code for generating random instances (with functions such as rand_profile).

In addition, there are various minor tweaks and adjustments. For example, in order to reduce namespace pollution, the use of unnecessary accessors has been deprecated. So instead of using, e.g., graph(C) on a Conflicts constraint, you should now use C.graph.