Upgrade to theorist 0.13.0 to rename Signal::flatMapLatest -> ::switch

Shorter, simpler, less intimidating.

package.json

@@ -50,7 +50,7 @@
     "temp": "0.5.0",
     "text-buffer": "0.12.0",
     "underscore-plus": "0.6.1",
-    "theorist": "~0.12.0",
+    "theorist": "~0.13.0",
     "delegato": "~0.4.0",
     "mixto": "~0.4.0"
   },

src/pane-container-model.coffee

@@ -14,7 +14,7 @@ class PaneContainerModel extends Model
   previousRoot: null
 
   @behavior 'activePaneItem', ->
-    @$activePane.flatMapLatest (activePane) -> activePane?.$activeItem
+    @$activePane.switch (activePane) -> activePane?.$activeItem
 
   constructor: ->
     super

src/pane-model.coffee

@@ -17,7 +17,7 @@ class PaneModel extends Model
 
   @behavior 'active', ->
     @$container
-      .flatMapLatest((container) -> container?.$activePane)
+      .switch((container) -> container?.$activePane)
       .map((activePane) => activePane is this)
       .distinctUntilChanged()