Convert badge list into Markdown table in README.md
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master | flake8 --diff`
- [ ] whatsnew entry

Also correct some badge links

@gliptak can you past a screen shot of what this looks like.
 @jreback  see https://github.com/gliptak/pandas/blob/patch-1/README.md

![screenshot from 2016-03-29 13 19 18](https://cloud.githubusercontent.com/assets/1217238/14122481/e0e173be-f5b0-11e5-8f3e-6ba945f81e3f.png)

There seems to be a visual glitch at the top of the table
 oh, so this is equiv of the html that we had before (which I ripped off).

what is the glitch?
 The "glitch" is a way to have an empty table header in Markdown. Comments on improvements are welcome :)
 If we can't have an empty table header in markdown, I would stick with HTML.
 How about a title (Description/Badge)? Or just have them in a row like most projects do:
https://github.com/xmlrunner/unittest-xml-reporting
https://github.com/kennethreitz/requests
 I think the rows are bad looking
much prefer he table
 let's leave the existing. of course if a markdown version is better (but preserves the structure), then pls re-open.
