COMPAT: drop suppport for python 2.6, #7718
closes #8760
closes #7718 

any complaints, comments, objections?
 :smile:  `compat` will get 400 lines shorter
 oh do I need to things out?
 `OrderedDict` and `Counter`
 This came up on the scikit-learn mailing list last week. I don't think they've come to a decision yet.

If we are approaching a 1.0 this year we should think about what we want to support indefinitely. I _think_ that's an argument for dropping 2.6.

Also, dict comprehensions :raised_hands:
 yes, I need to make an issue for what we want to _add_ (also can use things like `.assertGreater` and such in testing).
 @kawochen turned out to be 478 lines! (unless I took out too much)
 puzzled while `ChainMap` is not in 2.7. It _says_ it has it, but not when I look. oh well.
 ```
In [115]: from ConfigParser import _Chainmap as ChainMap
```
 wow, that's an odd place to have it!
 If you search for 26, you will find a few more places that can be tweaked (e.g. windows build script)
 @kawochen thanks.

updated
 bombs away
