pony-indent now behaves like other indent-line-functions.

In Emacs, the point moves to the end of indentation if the point came
before the first non-whitespace character in a line. Otherwise, the
point stays put, relative to the text.
Bind default-directory instead of using cd

The way `cd' was being used was clobbering the `default-directory'
setting of whichever `.py' file the pony functions were called in.
For most seen purposes (namely `shell-command-*' functions) just
let-binding `default-directory' should be enough to ensure that the
commands are executed in the correct directory.
Merge branch 'sfllaw/master'

Conflicts:
	src/pony-mode.el
Move to beginning of line before indent

If we don't go to the start of the line before checking what kind of
indentation we need we will be calculating a possible different
indentation value depending on the location of `point'.