IdenticonSvg v0.9.2 released, now with padding and much smaller SVG output

Thanks to some prodding by ku1ik on the Elixir Forum thread of IdenticonSvg, I put in some effort to implement three features that were long missing:

1. Automatic background color: you can now pass the argument :basic for basic color complementarity, :split1 for the first option of split complementarity, or :split2 for the second one. Passing nil sets the background to transparent, as before.

2. Padding: you can now pass an integer argument for the padding width, in terms of “blocks”. So, if size is 5 and padding is 1, the total size of the resulting SVG file is 7x7 blocks.

3. File size reduction: the resulting SVG files are now much smaller, as the naive array of foreground and background <rect> elements is replaced by a <path> with the content of its d attribute written in a compact manner. The background results from a mask. The output is now typically way less than one kilobyte.

The result is v0.9.2 on Hex.