ENH: add basic postgresql support to io.sql
I added in basic postresql support

Thanks for the contribution, unless @hayd wants to do this now, probably would push this to 0.14 (planning on a release candidate for 0.13 in the next few days). We are working on refactoring sql for the 0.14 release so hopefully we can incorporate some of this.
 sounds good, I could always lend a hand if he would like some help with postgresql there.  I'd really like to see psycopg2.copy_from method make it into 0.14
 I will absolutely take you up on that :). 
 i just imported an 18 column, 54k row dataframe using that commited code, took 20 mins to update my remote server using executemany, bulk inserts would be a very nice thing to have
 Btw, maybe easier to do would be to select subset of columns you care
about, then doing df.values.T, convert to list of lists and then pass to
executemany. (unless it can already work with ndarray). Don't have a
computer in front of me to test with right now though.
 @jtratner, @hayd, there's a jungle of sql PRs to sort through, help?
 We need one committer to take charge of this - I think my alternative
caused this to go off track. @hayd willing to do that?
 I'm game to get back on top of this, I think we got stuck bike shedding before, and ought to push forward hard for 0.14.
 I made bit of a mess of this with all these commits, I continued adding postgresql copy support to sql_legacy.py in PR #5323. Hope this helps some
 @rla3rd, does that mean this is superceded by #5323 and can be closed?
 If sql.py is to become sql_legacy.py in upcoming versions, and sql.py migrates to sqlalchemy under the hood, then yes, it is superseded by #5323.  I havent really done any work under the hood using sqlalchemy yet.
 @mangecoeur, perspective re #5950?
 @y-p this is superceded by the sqlalchemy support, we keep sqlite and mysql only for legacy support (since these were the only ones supported before)
 @rla3rd acknowledged that the new SQL functionality in 0.14.0 supercedes this.
Rather then having two ways to dath same things, we'll stick to the more general one in #5950.

closing. Thanks for the PR none the less @rla3rd .
