Meaning even "40" gets interpreted as the string "40", a category named
"40".

This is because SVG paths are always strings, so there is no practical
way of indicating a number was meant and not a numeric string when
specifying SVG paths (sure they could be wrapped in escaped quotes but
not today). So when a number is encountered in an SVG (i.e., it is a
numeric string), then it is converted to a number so that it is
interpreted as an index into layout.categoriesarray.

This made the dragging "jump" when categories were named numeric strings
as the strings were all of a sudden interpreted as indices. Lets see if
we can't make the pesky shapes test pass some other way.

Unfortunately the drag bug is back...

This keeps the tests passing and the correct behaviour when
categories are numeric strings.

good thing there's a test for this (bad thing that that is jasmine's way
of running one test)

with numeric string categories.