doc on `muDIC.vlab.rosta_speckle`

[edwardando]

in the docstring says the dot size is int bounded by 0 and 1 but the default value is 4!!!

 Parameters
 ----------

 size : tuple
     The image size as a tuple of integers
 dot_size : int
     The size of the dots [0,1]
 density: float, int
    How packeg with dots the speckle should be
 smoothness: float, int
    The degree of smoothing applied to the binary speckle

[edwardando]

plus there is mention of a layers kwarg which doesn't seem to exist any more...