Readme should have usage snippet

[fkiraly]

I would strongly suggest, the readme should have a usage vignette, e.g.,

from rolch.model import Foo
from rolch.data import load_bar
from rolch.prettyplot import veryprettyplot

X, y, X1, y1, X2, y2 = load_bar()
m = Foo()
m.fit(X, y)
y_pred = m.predict(X1)
m.update(X1, y1)
y_pred2 = m.predict(X2)

veryprettyplot(everything)

[simon-hirsch]

Good point!
Note to self: keep in mind for #21

[BerriJ]

This was implemented in #21