Update id_dist to version 0.4

Downloaded from http://tygert.com/software.html

Signed-off-by: Andreas Kloeckner <inform@tiker.net>
DOC: sparse: add the function 'find' to the module-level docstring
Fix reference computation in ID rank estimation to use relative rank

Signed-off-by: Andreas Kloeckner <inform@tiker.net>
MAINT: update pip wheelhouse for installs

Astropy wheelhouse no longer being used by astropy; switch to Rackspace
container.
Use the 2-norm in the rank estimation test

Signed-off-by: Andreas Kloeckner <inform@tiker.net>
Fix test for matrix-free rank estimation (as recommended by Ken Ho)

Signed-off-by: Andreas Kloeckner <inform@tiker.net>
Merge pull request #3843 from inducer/upgrade-to-id-dist-0.4

Update id_dist to version 0.4
ENH: cluster: rewrite and optimize hierarchy in Cython
Merge pull request #3860 from WarrenWeckesser/add-find-to-mod-doc

DOC: sparse: add the function 'find' to the module-level docstring
Merge pull request #3866 from matthew-brett/update-wheelhouse

MAINT: update pip wheelhouse for installs
Merge pull request #3792 from richardtsai/rewrite_hierarchy

ENH: cluster: rewrite hierarchy in Cython