ENH + BUG: insert of new values for axis parameter on pandas.DataFrame.quantile
closes #9543

I added the values "index" and "columns" for the axis parameter of the method pandas.DataFrame.quantile().
Also, there was no check on the value inserted for axis. E.g. if 2 or "foo" was inserted, no ValueError() was raised.
I added a basic check.

Thanks 

you don't need all this.

`axis = self._get_axis_number(axis)` will suffice

mainly need to add a test
 You are right. I am correcting it.
Thanks
 I corrected it and I implemented a basic test. In case tell me if I did any mistake.
Thanks
 I finally had the time to complete my PR with the Travis CI build. Now what have I to do? (it is my first PR)
 this looks fine. can you add a release note for 0.17.0 in the API section? ping when travis is green.
 Hi @jreback 
Have I to modify this file: https://github.com/pydata/pandas/blob/master/doc/source/release.rst
?
Second, when you say "can you add the issue number here" (see comment above) it means I should write something like:

`# Unit test for #9544`

Thanks
 @fbrundu this the file to which to add release notes: https://github.com/pydata/pandas/blob/master/doc/source/whatsnew/v0.16.2.txt

(we're actually going to release 0.16.2 before 0.17, and this can go in there)

As for the issue number, yes that would be fine. Something as simple as  `# GH9544` would be enough.
 @jreback travis is green but git tells me merge conflicts
let me know
 merged via https://github.com/pydata/pandas/commit/c0917de763d0c1369124f52bcaa18fb3fb36f05f

thanks!
