Fill out some new docs

docs/guide/existing-game.md

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+**TODO**
+
+## Summary
+* Can port as much or as little of your game as you like
+    * Rojo can manage just a slice of your game!
+* Some Roblox idioms aren't very well supported
+    * Redundant copies of scripts don't work well with files

docs/reference/full-vs-partial.md

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+Rojo is designed to be adopted incrementally. How much of your project Rojo manages is up to you!
+
+There are two primary categories of ways to use Rojo: *Fully Managed*, where everything is managed by Rojo, and *Partially Managed*, where Rojo only manages a slice of your project.
+
+## Fully Managed
+In a fully managed game project, Rojo controls every instance. A fully managed Rojo project can be built from scratch using `rojo build`.
+
+Fully managed projects are most practical for libraries, plugins, and simple games.
+
+Rojo's goal is to make it practical and easy for _every_ project to be fully managed, but we're not quite there yet!
+
+### Pros
+* Fully reproducible builds from scratch
+* Everything checked into version control
+
+### Cons
+* Without two-way sync, models have to be saved manually
+    * This can be done with the 'Save to File...' menu in Roblox Studio
+    * This will be solved by Two-Way Sync ([issue #164](https://github.com/LPGhatguy/rojo/issues/164))
+* Rojo can't manage everything yet
+    * Refs are currently broken ([issue #142](https://github.com/LPGhatguy/rojo/issues/142))
+
+## Partially Managed
+In a partially managed project, Rojo only handles a slice of the game. This could be as small as a couple scripts, or as large as everything except `Workspace`!
+
+The rest of the place's content can be versioned using Team Create or checked into source control.
+
+Partially managed projects are most practical for complicated games, or games that are migrating to use Rojo.
+
+### Pros
+* Easier to adopt gradually
+* Integrates with Team Create
+
+### Cons
+* Not everything is in version control, which makes merges tougher
+* Rojo can't live-sync instances like Terrain, MeshPart, or CSG operations yet
+    * Will be fixed with plugin escalation ([issue #169](https://github.com/LPGhatguy/rojo/issues/169))

mkdocs.yml

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   - Guide:
     - Installation: guide/installation.md
     - Creating a Game with Rojo: guide/new-game.md
-    # - Moving an Existing Game to Rojo: guide/existing-game.md
+    - Porting an Existing Game to Rojo: guide/existing-game.md
     - Migrating from 0.4.x to 0.5.x: guide/migrating-to-epiphany.md
   - Reference:
+    - Fully vs Partially Managed Rojo: reference/full-vs-partial.md
     - Project Format: reference/project-format.md
     - Sync Details: reference/sync-details.md
   - Rojo Alternatives: rojo-alternatives.md