feedback?

Hey everybody, I'm interested in getting feedback on the API. Here are a couple options...

```
# reza's version

from tuning import estimate

b, r2 = estimate(X, y)
b, r2 = estimate('file1.csv', 'file2.csv')

# daniel's version

from tuning import estimate, convert

X, y = convert('file1.csv', 'file2.csv')
b, r2 = estimate(X, y)
```

What do people think? 🎅 🎱 🎉 

@msarvestani?
