WIP: Server plugins via rlua (Lua 5.3) (#125)

* Add 'plugins' field to project and add rlua

* Scaffold out new SnapshotContext type (again) with plugin state

* Almost functional snapshot system with rlua proof-of-concept

* Gate plugin config on 'plugins-enabled' feature, tell Travis to test all features

* Guard remaining plugin setup code behind feature

* Bump minimum version to 1.33, should've caught this before

* Whoops, latest Rust is 1.32, not 1.33

server/src/snapshot_reconciler.rs

@@ -64,7 +64,7 @@ impl InstanceChanges {
 
 /// A lightweight, hierarchical representation of an instance that can be
 /// applied to the tree.
-#[derive(Debug, PartialEq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct RbxSnapshotInstance<'a> {
     pub name: Cow<'a, str>,
     pub class_name: Cow<'a, str>,
@@ -73,6 +73,22 @@ pub struct RbxSnapshotInstance<'a> {
     pub metadata: MetadataPerInstance,
 }
 
+impl<'a> RbxSnapshotInstance<'a> {
+    pub fn get_owned(&'a self) -> RbxSnapshotInstance<'static> {
+        let children: Vec<RbxSnapshotInstance<'static>> = self.children.iter()
+            .map(RbxSnapshotInstance::get_owned)
+            .collect();
+
+        RbxSnapshotInstance {
+            name: Cow::Owned(self.name.clone().into_owned()),
+            class_name: Cow::Owned(self.class_name.clone().into_owned()),
+            properties: self.properties.clone(),
+            children,
+            metadata: self.metadata.clone(),
+        }
+    }
+}
+
 impl<'a> PartialOrd for RbxSnapshotInstance<'a> {
     fn partial_cmp(&self, other: &RbxSnapshotInstance) -> Option<Ordering> {
         Some(self.name.cmp(&other.name)