v0.3.0

Main updates:

• switched to world coordinates to allow for easier multimodal T1/dMRI display
• added support for ROIs to show seeds/inclusions used in tractography
• added actor list toggle to simplify removing/adding items in the viewer
• fixed bugs related to tract display with surfaces
• allow loading of multiple .trk files simultaneously

Full Changelog: v0.1.0...v0.3.0