MNT: Change minconda URL and env spec

All of my [travis builds are erroring out](https://travis-ci.org/mwaskom/seaborn/jobs/20024477). I think this might be due to the conda version being a bit stale now. 

This is just me taking a stab fixing that.

Relevant portion of the travis log:
```
Extracting packages ...
 |                                                                        |   0%
[freetype            ] |################                                  |  33%
[imaging             ] |#################################                 |  66%
[jpeg                ] |##################################################| 100%
[      COMPLETE      ] |##################################################| 100%

Linking packages ...
[      COMPLETE      ] |                                                  |   0%
[freetype            ] |################                                  |  33%
[imaging             ] |#################################                 |  66%
[jpeg                ] |##################################################| 100%
[      COMPLETE      ] |##################################################| 100%

travis_fold:end:install.3
travis_fold:start:install.4
$ conda install --yes ipython==1.1.0 pyzmq numpy scipy nose matplotlib pandas statsmodels scikit-learn
Error: Unsatisfiable package specifications
Hint: numpy 1.7* has a conflict with the remaining packages

The command "conda install --yes ipython==1.1.0 pyzmq numpy scipy nose matplotlib pandas statsmodels scikit-learn" failed and exited with 1 during install.

Your build has been stopped.
```