In Python 3, the default source file encoding is UTF-8.

Indexing article no longer exists

* PEP 8: "Imports should usually be on separate lines"
* Where modified, sort imported modules alphabetically
* Clean-up unused imports from these expanded lines

As numpy is Python 3 only, these import statements are now unnecessary
and don't alter runtime behavior.

Previously the constants at the top of the page said words to the effect of "use the one at the bottom of this page instead".
Let's just show users those ones first to start with.

This commit only re-orders these constants, it does not change any of the descriptions, despite the diff appearing to show that