chore(build): execute pub get only if a pubspec.yaml changed and run dart analyzer on all dart files

`pub get` is now only executed when the `pubspec.yaml` in the `modules`
folder is different than the `pubspec.yaml` in the `build/dart` folder.

Generates the file `build/dart/_analyzer.dart` that imports all modules
to run `dart analyzer` against all of them. The build will fail whenever
there are errors, warnings or hints in `dart analyzer`.

Changes the sources so that `dart analyzer` does not report any
error, warning or hint.

Closes #40

modules/core/src/annotations/directive.js

@@ -1,19 +1,19 @@
-import {Type} from 'facade/lang';
-import {ElementServicesFunction} from './facade';
+// import {Type} from 'facade/lang';
+// import {ElementServicesFunction} from './facade';
 import {ABSTRACT} from 'facade/lang';
 
 
-@ABSTRACT
+@ABSTRACT()
 export class Directive {
 	constructor({
       selector,
       lightDomServices,
       implementsTypes
-    }:{
+    }/*:{
       selector:String,
       lightDomServices:ElementServicesFunction,
       implementsTypes:Array<Type>
-    })
+    }*/)
   {
     this.lightDomServices = lightDomServices;
 		this.selector = selector;

modules/core/src/annotations/facade.dart

@@ -1,3 +1,5 @@
+library core.annotations.facade;
+
 import 'package:di/di.dart' show Module;
 import '../compiler/element_module.dart' show ElementModule;
 

modules/core/src/annotations/template_config.js

@@ -1,4 +1,4 @@
-import {Type, List} from 'facade/lang';
+// import {Type, List} from 'facade/lang';
 
 export class TemplateConfig {
   constructor({
@@ -6,11 +6,11 @@ export class TemplateConfig {
       directives,
       formatters,
       source
-    }: {
+    }/*: {
       url: String,
       directives: List<Type>,
       formatters: List<Type>,
       source: List<TemplateConfig>
-    })
+    }*/)
   {}
 }

modules/core/src/compiler/compiler.js

@@ -1,6 +1,6 @@
 import {Future, Type} from 'facade/lang';
 import {Element} from 'facade/dom';
-import {ProtoView} from './view';
+//import {ProtoView} from './view';
 import {TemplateLoader} from './template_loader';
 import {FIELD} from 'facade/lang';
 
@@ -19,7 +19,7 @@ export class Compiler {
    *   - don't know about injector in deserialization
    *   - compile does not need the injector, only the ViewFactory does
    */
-  compile(component:Type, element:Element/* = null*/):Future<ProtoView> {
+  compile(component:Type, element:Element/* = null*/):Future/*<ProtoView>*/ {
     return null;
   }
 

modules/core/src/compiler/template_loader.js

@@ -1,11 +1,11 @@
 import {Future} from 'facade/lang';
-import {Document} from 'facade/dom';
+//import {Document} from 'facade/dom';
 
 export class TemplateLoader {
 
   constructor() {}
 
-  load(url:String):Future<Document> {
+  load(url:String):Future/*<Document>*/ {
     return null;
   }
 }

modules/core/src/life_cycle/life_cycle.js

@@ -4,7 +4,10 @@ export class LifeCycle {
 
   @FIELD('final _changeDetection:ChangeDetection')
   @FIELD('final _onChangeDispatcher:OnChangeDispatcher')
-  constructor() {}
+  constructor() {
+    this._changeDetection = null;
+    this._onChangeDispatcher = null;
+  }
 
   digest() {
     _changeDetection.detectChanges();