Andrew/old api additions

[ayjayt]

@emilykl

This PR includes some functions

import kaleido

kaleido.calc_fig(fig, opts={}, topojson="")
kaleido.calc_fig_sync(fig, opts={}, topojson="")
kaleido.write_fig_sync(...) # same as non sync
kaleido.write_fig_from_object_sync(...) # same as non sync

If one _sync works they all work, they uses a factory function, but I haven't tested them yet.

This is marked it in its changelog as rc8.

[ayjayt]

This now depends on #264

And the slated version upgrade for this is rc8.