Mutable bytes proposal (compromise)

Once again I find myself regretting a posting made late at night.  I've
moved the proposal to remove tuples
http://prothon.org/wiki?pagename=ImmutableObjectsNoTuples to the rejected
list for 1.0.

I've changed the mutable bytes proposal
http://prothon.org/wiki?pagename=MutableBytes to now recommend having only
the one mutable Bytes type and to use the setting of individual objects to
immutable to use them as keys for dictionaries.  

I don't think bytes types will be used as dictionary keys often enough to
warrant having an immutable type just for that purpose.  You also have the
option of converting a Bytes object to a latin-1 string for a dictionary key
if the immutable Bytes option is too weird for your taste.

I think this compromise also works in that we have the String type as
immutable and the Bytes type as mutable so they sort of pair off that way.

If you don't agree with this compromise let me know.