Fix specs

spec/command-installer-spec.coffee

@@ -9,9 +9,7 @@ describe "install(commandPath, callback)", ->
   destinationPath = path.join(directory, 'bin', 'source')
 
   beforeEach ->
-    spyOn(installer, 'findInstallDirectory').andCallFake (callback) ->
-      callback(directory)
-
+    spyOn(installer, 'getInstallDirectory').andReturn directory
     fs.removeSync(directory) if fs.existsSync(directory)
 
   describe "on #darwin", ->

src/command-installer.coffee

@@ -23,6 +23,9 @@ unlinkCommand = (destinationPath, callback) ->
       callback()
 
 module.exports =
+  getInstallDirectory: ->
+    "/usr/local"
+
   install: (commandPath, commandName, callback) ->
     if not commandName? or _.isFunction(commandName)
       callback = commandName
@@ -33,7 +36,7 @@ module.exports =
         console.warn "Failed to install `#{commandName}` binary", error
       callback?(error, sourcePath, destinationPath)
 
-    directory = "/usr/local"
+    directory = @getInstallDirectory()
     if fs.existsSync(directory)
       destinationPath = path.join(directory, 'bin', commandName)
       unlinkCommand destinationPath, (error) ->