DOC: ref / val caveat, point at pandas methods
This in part addresses #3340.

I added a few comments in the doc that point users ad using the pandas
at, iat, loc, iloc, etc. methods and included an example similar to
the one exposed in #3340 that addresses some of the reference / value
intricaies encountered with pandas and numpy objects.

To make things clear I selected a rather verbose style.
Let me know if this is over the top ;-)

looks good, I would add the notes using the rst `note` directive, makes them stand out (with the lines around them)...my 2c

like this

```
.. note::

   The recent addition of ``.loc`` and ``.iloc`` have enabled users to be quite
   explicit about indexing choices. ``.ix`` allows a great flexibility to specify
```
 @jreback thanks for your pointer. Just pushed another iteration over the text with .rst directives.
 next tip:rebase these to a single commit (you don't always want to do this, but in this case since
these are just changes it makes sense)

`rebase -i <commit>`

use the commit 1 previous to your first commit
you can also do `HEAD~4` which in this case will get you that commit

then either squash (s) / fixup (f) the commits to form a bigger one (s preservers the commit message, f does not)

then

`git push myfork branch_name -f`

will replace all of these commits with a new one.... (w/o the f it just appends new commits)
 @jreback here we go ;-)
 @dengemann , can you wrap that text to match the rest of the document?
That's easier to revise in a text editor later on.
 Yeah, I forgot about about that, sorry. Hold on.

On Sat, Apr 20, 2013 at 11:54 AM, y-p notifications@github.com wrote:

> @dengemann https://github.com/dengemann , can you wrap that text to
> match the rest of the document?
> That's easier to revise in a text editor later on.
> 
> —
> Reply to this email directly or view it on GitHubhttps://github.com/pydata/pandas/pull/3399#issuecomment-16701562
> .
 Wrapped, rebased.
 @dengemann I moved the view vs copy example to consolidate with the section we had for it; I think should actually expand this example to show a proper assignment using .loc/.iloc (using your example), want to do this?
 >  I moved the view vs copy example to consolidate with the section we had for it;

Thanks!

> I think should actually expand this example to show a proper assignment using .loc/.iloc (using your example), want to do this?

Sure, I might find some time tonight.
