Version 0.3

This Christmas time release is a big milestone for SpiceGUI because 1.0 is nearer, so stay tuned for new releases!

New features:

• Improved first-use experience (5890010)
• Register SpiceGUI as schematic and netlist MIME type handler (d97b9d5, aedb83a, 06e8c23)
• Better syntax highlight (7529f25, 42f491a, c96baa1)
• Non-blocking circuit simulation. GUI doesn't freeze if ngspice takes time to complete the operation (74a84c4)
• Better identification of axis magnitudes in plots (b3ba579)
• Python 3 support (5381f9e)
• AppData file included in distribution for software-center-like applications (aeb16fb)
• Minor tweaks and polishments!