Cosmetic cleanning.
Fine adjust on the fitt.v_circular()

The initial values for the translating should be near zero, otherwise
  it starts already with some distortion.
Changing the range of the CL ring parameters.
Reducing lambda.
Increasing a minor version. Some improvements, fine tunning.
Don't like zero as initial guess.

Temporary solution to don't let p0 starts with 0. The adjusting system
don't like it.
vortex_3Dpatches moved back to ringslegacy
Increasing the default lambda back to 1e-2.

Looks like 1e-3 still allows some over-fitting.
I'm back to don't set initial p0 based on the dataset.

I still think it has some future here, but need to work on it.
Moving some comments about CartonLegras from rings.py to fitt.py
Class Ring now allows input (x,y) or (Lon, Lat).
Working on the drifter_sample fucntion.
Fixing a minor bug. % is the comment symbol on the LaTeX, not here.
Heavy changes, migrating Ring to RingCenter.

A new concept, RingCenter will be the base class, working on (t, x, y,
u, v). And other classes will be build on the top, using that to handle
other formats, like (datetime, Lon, Lat, u, v).
Adjusting the procedures inside rings.Ring to use self.center .
Just organizing, and using the auto var.
RingCenter works, but need some cleaning.
Cleanning RingCenter and starting RingCenterFlex
Medium level upgrade. Now is RingCenter, instead of Ring.

The center is now estimated by the class RingCenter, which expects the
default mks input (t,x,y,u,v).

The class RingCenterFlex will handle the LatxLon and datetime inputs.