Organizing and bugfix to set ring's velocity structure.

To estimate the distortion of the data xr, yr, I must use
self.input['t'], not self.data['t'].
RingCenterFlex now define t from datetime.
Forgot to remove a pdb.set_trace() call.
Bugfix on time handling and now include self.center['datetime'].
Adjusting set_xy inside the RingCenterFlex
RingCenterFlex now works with (Lat,Lon) or (x,y).

Once I migrated the basic system to the RingCenter class, I used the
  fundamental variables (t, x, y, u, v). Now the RingCenterFlex works
  with ( (t|datetime), ((Lat, Lon) | (x, y)), u, v).
Minor version upgrade, RingCenterFlex is working.
Including the function sampler()

Part of the estimate_error, related to the actual sampling, was moved
  to a new function sampler().
Working on the montecarlo.sampler()
Fixing the drunken_drive()
montecarlo() now uses progressbar, if it's available.
Minor version upgrade.
Moving EddyData and EddyDataVar back to ringslegacy
Ignoring *.h5
Including Acknowledgmets