Release a 1.0 version

[obsgolem]

This library appears to be the de-facto standard for complex numbers. Downstreams include ndarray and nalgebra. I just ran into an issue where ndarray is using an older version of approx, where if you turned on its num-complex feature it tried to use an older version of num-complex. If you aren't planning on making breaking changes then it would be nice if you could bump to a 1.0 version so that feature additions don't require upstreams to bump their versions. See also brendanzab/approx#70.

[cuviper]

Just as approx cited num-complex, I must cite our public dependencies as well. It's uncertain about num-traits (which I also control), but rand does seem like it will eventually want to update to 0.9 and later.