Rename vfs -> memofs across the codebase

memofs/README.md

@@ -0,0 +1,18 @@
+# vfs
+Implementation of a virtual filesystem with a configurable backend and file watching.
+
+memofs is currently an unstable minimum viable library. Its primary consumer is [Rojo](https://github.com/rojo-rbx/rojo), a build system for Roblox.
+
+### Current Features
+* API similar to `std::fs`
+* Configurable backends
+    * `StdBackend`, which uses `std::fs` and the `notify` crate
+    * `NoopBackend`, which always throws errors
+    * `InMemoryFs`, a simple in-memory filesystem useful for testing
+
+### Future Features
+* Hash-based hierarchical memoization keys (hence the name)
+* Configurable caching (write-through, write-around, write-back)
+
+## License
+memofs is available under the terms of the MIT license. See [LICENSE.txt](LICENSE.txt) or <https://opensource.org/licenses/MIT> for more details.