Release 0.5.0 stable

[LPGhatguy]

This is a big release, so I'm going through the PR process to make sure we aren't missing anything.

There is one minor compatibility-impacting change in this release and one-ish bug fix since 0.5.0 alpha 13.

After this release goes out, we will:

• Mark Rojo 0.4.x as officially end-of-life
• Update the VS Code plugin to kick people off of Rojo prereleases and onto the 0.5.x stable release track
• Create a 0.5.x branch off of master for future 0.5.x releases
• Merge Major Subsystem Rewrite (Reconciler Mk5) #217 (new-reconciler branch) into master, kicking off 0.6.0 with better foundations
• Run Rustfmt and Clippy over the resulting codebase!

Known Issues

• Rojo drops Ref properties #142: Rojo still does not support ref properties, this will be fixed in 0.6.x
• "supplied instant is later than self" #215, Too many open files (os error 24) #214, Deleting file in VSCode does not sync with Studio #213, Ending folder name w/ .lua causes rojo to become unresponsive in specific cases #193, Moving folder within partition while live won't sync #132: Various issues around changes being dropped that we weren't quite able to pinpoint. After Major Subsystem Rewrite (Reconciler Mk5) #217 merges, we'll be working on fresh foundations, which means fresh bugs!