Cannot create Series from dict with unorderable keys
It appears that it is not possible to create a Series from a dict whose keys are unorderable.  `Series.__init__` unconditionally attempts to sort a dict that is passed as the data.  This means that, for instance, you can't simply create a Series from a dict whose keys are complex numbers:

`>>> pandas.Series({1j: 1, 2j: 2})
Traceback (most recent call last):
  File "<pyshell#33>", line 1, in <module>
    pandas.Series({1j: 1, 2j: 2})
  File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\core\series.py", line 444, in __new__
    index = Index(sorted(data))
TypeError: no ordering relation is defined for complex numbers`

It's possible to work around the problem by passing the dict values as the data and the keys as the index, but this is cumbersome.  It would be nice to just have an argument to Series() that tells it not to try to sort the index.
