Add overrides pprt in bower.json for plain CSS

Due to https://github.com/twbs/bootstrap/blob/v3.3.5/bower.json#L18
Wiredep need the right file in main pprt

Author: zckrs

app/templates/_bower.json

@@ -56,6 +56,16 @@
   "devDependencies": {
     "angular-mocks": "<%- props.angularVersion %>"
   },
+<% if (props.cssPreprocessor.key === 'none' && props.ui.key === 'bootstrap') { -%>
+  "overrides": {
+    "bootstrap": {
+      "main": [
+        "dist/css/bootstrap.css",
+        "dist/js/bootstrap.js"
+      ]
+    }
+  },
+<% } -%>
   "resolutions": {
 <% if (props.jQuery.key === 'jquery1') { -%>
     "jquery": "~1.11.3",

test/template/test-bower.js

@@ -177,4 +177,12 @@ describe('gulp-angular bower template', function () {
     result.should.match(/traceur-runtime/);
   });
 
+  it('should add overrides pprt for css bootstrap', function() {
+    model.props.ui.key = 'bootstrap';
+    model.props.cssPreprocessor.key = 'none';
+
+    var result = bower(model);
+    result.should.match(/overrides/);
+    result.should.match(/dist\/css\/bootstrap.css/);
+  });
 });