Fixed ref to old scitools.org page.
Merge pull request #441 from pp-mo/scitools_pagefix

Fixed ref to old scitools.org page.
Added iris.tests.assertArrayAllClose for array testing with relative tolerance.
Merge pull request #440 from pp-mo/test_arrays_reltol

Added iris.tests.assertArrayAllClose
Add bilinear interpolation between rectilinear grids.