Coverage report includes bower components when using browserify

My angular project uses browserify and debowerify (for including bower components) and I've managed to get code coverage working, but it seems to include all of the bower components along with my own code. Does anyone have any idea what could be causing this?

Here is my karma.conf file:

```
'use strict';

module.exports = function (config) {
config.set({
basePath: './',

frameworks: ['browserify', 'mocha', 'chai', 'sinon'],

files: [
'./libs/angular/angular.js',
'./libs/angular-mocks/angular-mocks.js', // for angular.mock.module and inject.
'./app/**/*.js'
],

exclude: [],

preprocessors: {
'./app/**/!(*spec)*.js': ['browserify']
},

browserify: {
debug: true,
transform: ['debowerify', 'html2js-browserify', 'browserify-istanbul'],
extensions: ['.js']
},

reporters: ['spec', 'coverage'],
coverageReporter: {
type: 'html',
dir: './reports/coverage'
},

port: 9876,
colors: true,
logLevel: config.LOG_INFO,
autoWatch: true,
browsers: [
// 'Chrome',
'PhantomJS'
],

singleRun: false
});
};
```

Start with the karma.conf.js settings shown, especially the browserify preprocessor and the debowerify and browserify-istanbul transforms. Reproduce the coverage report and trace why bower components are instrumented. Done means the report includes the project's app code without including bower components.

Written by the indexing model from the issue text.