Fixes for #1000, to_string(), to_html() should respect col_space
Note that the semantics of `col_space`  are different in each case, characters vs. pixels,
but that's reasonable.

I hope this doesn't presage more html configuration via kwd arguments, yonder way
madness lies.

also, there's a discrepency between the docstring and [io.rst](https://github.com/pydata/pandas/blame/master/doc/source/io.rst#L671) (github doesn't seem to jump to the right line)
the first defines it as the width of the columns, the latter as the number of spaces between columns,
I adopted the former, since space between columns does not translate as easily to html.

_sigh_, also, `colSpace` has already been deprecated in favor of `col_space`, so
I would feel bad about deprecating `col_space` in favor of `min_col_width`.
I'll leave that decision to braver, fearless  souls.

closes #1000.
