0.1:

  * Fixed: removed discussion on k-nearest neighbor exclusion models which do
    not cover the lattice perfectly.

  * Fixed: extra assumption: particle configurations are determined by their
    defects.

  * Fixed: miscellaneous minor tweaks, formatting and typos.

  * Added: discussion about Lee-Yang zeros and their relation to the
    high-fugacity expansion.

  * Added: open problem: soft exclusion potentials.

  * Added: extended bibliography.

  * Changed: Particles in figures are now always centered on the lattice, not
    the dual lattice.

  * Changed: improved Makefile.