Use "coding:" instead of "encoding:" to specify file encoding

Using "-*- encoding:utf-8 -*-" doesn't really set the file encoding
for Emacs. It will even prompt the user when opening a compiled file:

  The local variables list in foo.mak.py
  contains values that may not be safe (*).

  Do you want to apply it?  You can type
  y  -- to apply the local variables list.
  n  -- to ignore the local variables list.

  !  -- to apply the local variables list, and permanently mark these
        values (*) as safe (in the future, they will be set automatically.)

    * encoding: utf-8

The problem is that Emacs looks for a file variable named "coding" and
it doesn't know about "encoding":

  http://www.gnu.org/software/emacs/manual/html_node/emacs/Specify-Coding.html

This is no doubt why Python recognizes "coding:" by itself:

  http://www.python.org/dev/peps/pep-0263/

This change makes the code generator output "# -*- coding:%s -*-" and
updates the documentation and examples to match this style.
Use Emacs compatible coding system

Emacs doesn't recognize "utf8" as a valid coding system. The correct
name is "utf-8". This is in line with the UTF-8 FAQ:

  http://www.cl.cam.ac.uk/~mgk25/unicode.html#utf-8

  The official name and spelling of this encoding is UTF-8, where UTF
  stands for UCS Transformation Format. Please do not write UTF-8 in
  any documentation text in other ways (such as utf8 or UTF_8), unless
  of course you refer to a variable name and not the encoding itself.
Fix docstrings to use "UTF-8" instead of "utf8"

The UTF-8 FAQ says this is the correct name for the encoding.

  http://www.cl.cam.ac.uk/~mgk25/unicode.html#utf-8

  The official name and spelling of this encoding is UTF-8, where UTF
  stands for UCS Transformation Format. Please do not write UTF-8 in
  any documentation text in other ways (such as utf8 or UTF_8), unless
  of course you refer to a variable name and not the encoding itself.
- changelog for Martin Geisler's coding/utf-8 fixes
- version bump 0.9.1