Using Polaris.Optimizers as docs suggest causes error

[shaqq]

Most docs suggest using this library like so:

Polaris.Optimizers.adam(0.005)

However, this causes an error, because the args expect a keyword list

** (FunctionClauseError) no function clause matching in Keyword.pop/3    
    
    The following arguments were given to Keyword.pop/3:
    
        # 1
        0.005
    
        # 2
        :learning_rate
    
        # 3
        0.001
    
    Attempted function clauses (showing 1 out of 1):
    
        def pop(keywords, key, default) when is_list(keywords) and is_atom(key)
    
    (elixir 1.15.7) lib/keyword.ex:1289: Keyword.pop/3
    (polaris 0.1.0) lib/polaris/optimizers.ex:109: Polaris.Optimizers.adam/1

Looks like this was intentional: 228f829

So this is an issue to update the docs 😄

[josevalim]

Please send a PR :)