Bug in abreu2010 function

Current code in emd.simulate.abreu2010: num = nonlin_deg * np.sin(nonlin_phi) / 1 + np.sqrt(1 - nonlin_deg**2)

Actual equation from the paper (I think): num = nonlin_deg * np.sin(nonlin_phi) / (1 + np.sqrt(1 - nonlin_deg**2))

Missing brackets change the resulting shape!

Also could be simplified to: num = nonlin_deg * np.sin(nonlin_phi) / (1 + factor)

Finally, in the docs Eq 9 is cited, but the above comes from Eq 7 in Abreu 2010.