Added area_exact and area_ellipse to statistics
Fixed failing tests
Added tests for area calculation
Added area to API docs
Implement exact area for PPVStatistic
Make dendrogram structure order deterministic
Renamed sorted_by_idx to _sorted_by_idx
Added test for PPV area_exact
Added ``area_exact`` for PPV cataloguing
Added PPVStatistic.area_exact to API docs
Fixed failing test
Try and ensure that metadata warnings only get raised once, and fixed a deprecation warning due to a change in the Astropy API
shape is no longer required for Structure.get_mask - Structures now store a reference to the parent dendrogram if they are attached to one.
Added a test of Structure._dendrogram inside existing tests
Fixed remaining calls to get_mask
Fix ellipse area to match plotted one
Fix test
Eliminate recursion in Structure.get_peak and Structure.sorted_leaves. Rename method
Merge pull request #83 from astrofrog/fix-get-mask

get_mask should default to shape of generating image
Merge pull request #72 from astrofrog/enforce-single-warning

On some platforms, warnings are repeated many times