Add a configuration/settings file

[xNul]

As this project has grown, I have found a lot of areas where a settings panel would be useful. For the time being editing the script should be fine, but eventually I wish to add a settings panel to the visualizer to ease that process. Before this happens, a design style needs to be determined and the GUI implemented (if it's decided there will be one).

Ideas:

• sample input size settings: 256, 512, 1024, 2048, custom
• tick distance slider (inside settings menu for default vis)
• screen ratio setting: 16/10, 16/9, 4/3
• fade options: toggle, turn off bloom, intensity slider (right side for louder
  songs, left for softer), auto
• more color options
• set fps cap. 0 = no cap. Works on Windows?
• switch visualization (maybe visualization-specific settings)
• window size persistence through program shutdowns

[xNul]

Adding a fully-fledged, good looking settings panel would decrease the simplicity of Drop significantly, be complex, require multiple libraries, and after all was said and done, probably wouldn't match the current style anyway. Therefore, I have decided to forgo the graphical portion.

With commit https://github.com/nabakin/drop/commit/eaf94810448e4479c80728ec3442d9849418a776, configuration file support has been added and this feature has now been added.