use browserify and watchify as peer and dev depedency

[oroce]

I saw the discussion in #14 so I did this pr.

To notify the users we could add the following snippet to the bin/cmd.js:

+try {
+  require.resolve('browserify');
+} catch (x) {
+  console.error('browserify is not install, run npm install browserify');
+  process.exit(1);
+}
run();

[royriojas]

Hi @oroce,

Thanks for the PR could you please add the snippet to warn users of this change?

[ruffle1986]

Just a little message correction: browserify is not installed

[oroce]

@royriojas I just added the snippet!

[royriojas]

Thanks @oroce merging it now