Make toml.py accept spaces in table names.

toml.py currently accepts spaces in key names, but raises an `Exception` on
table names with spaces in them.  This had to do with the first half of
`loads()` replacing the newline after a space-containing table name with a
space, thinking it was in an open array.

So, this was ok:

    >>> toml.loads('''\
    ... [a]
    ... x = 1
    ... ''')
    {'a': {'x': 1}}

But this was not:

    >>> toml.loads('''\
    ... [a b]
    ... x = 1
    ... ''')
    Traceback (most recent call last):
      File "<stdin>", line 4, in <module>
      File "toml.py", line 117, in loads
        raise Exception("Key group not on a line by itself.")
    Exception: Key group not on a line by itself.

Adding a flag to the tokenizing (?) portion of `loads()` to track when we are inside a table (or `arrayoftable` for that matter) seems to prevent [these lines](https://github.com/uiri/toml/blob/5ad4ccac3943a2522e92679a00cf8bcb0d1e1f8d/toml.py#L64-67) from causing `openarr` to decrement later (which results in the deletion of a newline).

This patch does not change any results from BurntSushi's test suite.