[BUG] default predicted slot for tSNE is set to a slot that doesnt exist

[grlloyd]

example:

M = tSNE()
predicted(M)

result:
"tnse"

this causes tSNE when part of a sequence to fail because

predicted(M)

Error in slot(obj, name) : 
  no slot of name "tsne" for this object of class "tSNE"

To work around this the predicted slot can be set when creating the object:

M = tSNE(predicted = 'Y')