fix(demo-app): resolve mapping paths in relative. (#566)

* Currently, the demo app is mapping its core and components absolutely (`/`), which is working perfectly for the served application
* This commit changes the absolute mapping paths to relative paths.
  This allows developers, to serve the demo-app also in sub-directories.

Also this is required for some bundlers, for example SystemJS Builder is not able to build a bundle of the demo app, with absolute paths, because the
baseURL may be different.

References #553

src/demo-app/system-config.ts

@@ -25,9 +25,9 @@ const components = [
 
 /** Map relative paths to URLs. */
 const map: any = {
-  '@angular2-material/core': '/core',
+  '@angular2-material/core': 'core',
 };
-components.forEach(name => map[`@angular2-material/${name}`] = `/components/${name}`);
+components.forEach(name => map[`@angular2-material/${name}`] = `components/${name}`);
 
 
 /** User packages configuration. */

src/e2e-app/system-config.ts

@@ -25,9 +25,9 @@ const components = [
 
 /** Map relative paths to URLs. */
 const map: any = {
-  '@angular2-material/core': '/core',
+  '@angular2-material/core': 'core',
 };
-components.forEach(name => map[`@angular2-material/${name}`] = `/components/${name}`);
+components.forEach(name => map[`@angular2-material/${name}`] = `components/${name}`);
 
 
 /** User packages configuration. */