Drop peer dep on loopback; add a runtime check

Replace peerDependency with a run-time check based on
`app.loopback.version`.

lib/executor.js

@@ -1,6 +1,7 @@
 var assert = require('assert');
 var _ = require('underscore');
 var loopback = require('loopback');
+var semver = require('semver');
 var debug = require('debug')('loopback:boot:executor');
 
 /**
@@ -13,6 +14,8 @@ var debug = require('debug')('loopback:boot:executor');
  */
 
 module.exports = function execute(app, instructions) {
+  assertLoopBackVersion(app);
+
   setHost(app, instructions);
   setPort(app, instructions);
   setApiRoot(app, instructions);
@@ -27,6 +30,22 @@ module.exports = function execute(app, instructions) {
   enableAnonymousSwagger(app, instructions);
 };
 
+function assertLoopBackVersion(app) {
+  var RANGE = '1.x || 2.x';
+
+  // app.loopback was introduced in 1.9.0
+  var loopback = app.loopback || {};
+  var version = loopback.version || '1.0.0';
+
+  if (!semver.satisfies(version, RANGE)) {
+    throw new Error(
+        'The `app` is powered by an incompatible loopback version %s. ' +
+        'Supported versions: %s',
+        loopback.version || '<1.9',
+      RANGE);
+  }
+}
+
 function setHost(app, instructions) {
   //jshint camelcase:false
   var host =

package.json

@@ -23,9 +23,10 @@
     "url": "https://github.com/strongloop/loopback-boot/blob/master/LICENSE"
   },
   "dependencies": {
-    "underscore": "^1.6.0",
+    "commondir": "0.0.1",
     "debug": "^0.8.1",
-    "commondir": "0.0.1"
+    "semver": "^2.3.0",
+    "underscore": "^1.6.0"
   },
   "devDependencies": {
     "loopback": "^1.5.0",
@@ -34,8 +35,5 @@
     "supertest": "^0.13.0",
     "fs-extra": "^0.9.1",
     "browserify": "^4.1.8"
-  },
-  "peerDependencies": {
-    "loopback": "1.x || 2.x"
   }
 }