Just suppress the spurious IndexError when it happens. Rely on the environments where the behavior doesn't fail until the upstream issue can be resolved. Fixes #201.

Merge pkg_resources.Environment.__getitem__() code cleanup (pull request #47 and subsequent changes).

Correct sort order by using list.sort with support for 'key' and 'reverse'. This method is less efficient, but allows the tests to pass.

Restore install._install with a comment to capture its requirement on earlier NumPy versions. Fixes #199.

--HG--
extra : amend_source : a76d060c98e0048506e5aadddd675151db9d273c

--HG--
extra : amend_source : 4efa6b87d3acaefebdfcc953e78a452ffc1f160d

--HG--
extra : amend_source : 20ab7547c8478eb084767fe701e627bdd462ba16

Better commented the code, especially the result caching & lazy distribution
list sorting strategies implemented there. Added several TODO comments
indicating things to look into there in the future.

General code cleanup:
 - stopped reusing the project_name variable for different purposes
 - added an assertion to detect corrupt distribution list caches

--HG--
extra : source : 86ef8f59ef4e1fc253c155b9ca0856497455372d

--HG--
extra : source : 32166eed1174dc565d903c81b9d99c292357aecc

--HG--
extra : source : ab82442e2205a4ab1016711e482388590688fa15