fix quarantine/ipy_editors.py

I wanted to use textmate with `%ed`, so I found this module. It needed a little work, but not too much.

fixes:
- uses string formatting instead of some old old `itpl` module
- doesn't use the deprecated ipyapi
- fully pep8 compliant
- better docstring

per @ellisonbg's [commit](https://github.com/ipython/ipython/commit/928c921bb501be285fb1e2d675cd1c4f512c0a5b) three years ago that moved it into quarantine, I _don't_ think this module should be actually removed from quarantine:

>Moving extensions to either quarantine or deathrow.
>When a module is moved to quarantine, it means that while we intend
>to keep it, it is currently broken or sufficiently untested that it
>can't be in the main IPython codebase.  To be moved back into the main
>IPython codebase a module must: 

>1. Work fully.
>2. Have a test suite.
>3. Be a proper IPython extension and tie into the official APIs.
>3. Have members of the IPython dev team who are willing to maintain it.

>When a module is moved to deathrow, it means that the code is either broken
>and not worth repairing, deprecated, replaced by newer functionality,
>or code that should be developed and maintained by a third party.

Since I've never used many of the editors -- and the code depends on the format in which they like their arguments when invoked from the shell -- I can't confirm that all the code works. (It does work for emacs, textmate and idle on osx). Also, it's not really clear how to test this module, since you would need to have all the editors installed.

But regardless, the current `ipy_editors.py` **assuredly** does not work, and the code in this PR works at least for some editors (on some platforms). So it's an improvement, no?