First pass at getting identification code working.

Local maximum and centroid-analysis seem to work (maybe even
in arbitrary dimensions)
Added to the sphinx documentation, tweaked docs
added intersphinx map for numpy
added band-pass filter
added example for identification code
Merge branch 'master' into iden
fixed transpose error.

ndimage and matplotlib disagree on (x, y) vs (y, x).  Embedded
necessary transposes so the user does not have to know this.
updated identification example to used off-axis points.
added test for identification code
Merge branch 'iden'