add two failing range tests
updating range.each to use only succ and <=>

* Except in the case of Symbols, which require String.upto. See
  https://github.com/ruby/ruby/blob/trunk/range.c#L755 for ref
mark range tests as xfail

It will fail until string.upto is implemented
adding Bill Mill to AUTHORS
fixing order list alphabetization (whoops)
properly handle symbol iteration in the absence of upto

* Also return self when done iterating
convert range tests to use each directly instead of through map
removing debugging code from test_range_symbols
assert that each string is a symbol
raise NotImplementedError if no block given to each

AFAIK there is currently no NotImplementedError defined in ruby, so
just raise it as a string for now
accept a block explicitly in range#each
remove unused import in test_rangeobject