2017.05 "Superfit"

New things:

• fit_curve, wrapper with common interface for curve_fit, odr, and other things implemented in lab.py.
• fit_oversampling, to fit a digital sampling of a costant value.
• format_par_cov.
• nextfilename.
• The argument sqerr of mme now accept a callable (main goal to ignore calibration error)

Deprecated functions:

• curve_fit_patched (update scipy!)
• fit_generic_xyerr, fit_generic_xyerr2 (use fit_curve)
• etastart, etastr (use Eta)