More efficient 'tell_many'

import adaptive

def f(x, offset=0):
    a = 0.01
    return x + a**2 / (a**2 + (x - offset)**2)

learner = adaptive.Learner1D(f, bounds=(-1, 1))
adaptive.runner.simple(learner, goal=lambda l: l.npoints > 200)

%%timeit
learner2 = adaptive.Learner1D(f, bounds=(-1, 1))
learner2.tell_many(*zip(*learner.data.items()))

%%timeit
learner2 = adaptive.Learner1D(f, bounds=(-1, 1))
for x, y in learner.data.items():
    learner2.tell(x, y)