svg support for generated plantuml images

[volc]

Hi Jayson,

what do you think about adding an additional falg in the preferences for the output format of the rendered image? :) something like:

{
    "viewer" : "Preview", // Preview, QuickLook, EyeOfGnome, WindowsDefaultViewer
    "format" : "svg", // png, svg, ascii
    "check_on_startup": true,
    "charset": null // Can be "UTF-8" - to support non-latin text in diagram
}

the plantuml library already has the appropriate methods for outputting svg images :)

[jvantuyl]

I would merge a patch that implemented this.

[evandrocoan]

Sublime Text does not render SVG, so using it would not help much:

1. No preview for svg sublimehq/sublime_text#556 No preview for svg

[jvantuyl]

The diagram plugin does support other viewers that do. ¯_(ツ)_/¯

[jvantuyl]

This was implemented in #59.