Updated README to use new API changes in python examples.
Changed IA_S3_... ENV variables to IAS3_...
Added `delete` option to `upload_file()` and `ia upload`, which deletes files after verify checksums of successful uploads.
use print() function in examples.
Added `six` package to requirements. `internetarchive` now has limited support for Python3.
 Fixes to the documentation presented when using the CLI.

PLEASE: Look over the changes before merging, to make sure they all look good.

_A summary of the changes_:
Fixes to README.rst:
-- fixed a mess-up in the example for "--glob", and a mess-up in the
   example for uploading
-- changed instructions for S3 keys from environmental variables to ia
   configure
-- changed the final example for "ia mine" to use "ia mine -"

Fixes to ia_list.py:
-- Changed the documentation for --columns to make it more obvious
   that any length list of comma separated columns was fine

Fixes to ia_metadata.py:
-- Fixed the doc on --exists, which somehow had some of it deleted

Fixes to ia_mine.py:
-- Mentioned in the usage that it can take stdin. Maybe that looks
   bad, though -- you decide.

Fixes to ia_search:
-- "--sort" can take multiple arguments. Added that to usage.

Multiple files:
-- Changed instructions to "pip install cython git+...=gevent"
   to just "pip install gevent" (which does work)
Merge branch 'master' of https://github.com/jjjake/ia-wrapper
(I had a bit of a mess-up with with using git, so I'm kinda confused as to the state of things, but I'm pretty sure everything is good.)

Conflicts:
	README.rst
Merge branch 'master' of https://github.com/fibn144/ia-wrapper
(Okay, I'm pretty sure that I'm passed the I'm-not-entirely-sure-
-what-git-did muddle.)

Conflicts:
	README.rst