Remove unused liveJs option

There do not appear to be any LiveReload client implementations that do
live JS reloading.

See also #107, which discusses
`livereactload` (which does offer live JS reloading in very specific
circumstances but does not appear to be a full livereload implementation) and [`issue 18 at
livereload-js`](livereload/livereload-js#18),
which points out that livereload-js does not do live js reloading.

livereload-js currently observes the [`liveCSS` and `liveImg`
options](https://github.com/livereload/livereload-js/blob/20e9c3a5a4e33d46f616741394130e93472adc2c/src/livereload.coffee#L93-L94),
but not `liveJs`.

lib/client.js

@@ -58,7 +58,6 @@ class Client extends events.EventEmitter {
         command: 'reload',
         path: file,
         liveCSS: this.options.liveCSS !== false,
-        liveJs: this.options.liveJs !== false,
         liveImg: this.options.liveImg !== false
       });
     }, this);

readme.md

@@ -153,7 +153,6 @@ See [gulp-livereload](https://github.com/vohof/gulp-livereload) repo.
 - `cert`          - Option to pass in to create an https server
 - `pfx`           - Can also be used to create an https server instead of `key` & `cert`
 - `liveCSS`       - LiveReload option to enable live CSS reloading (defaults to true)
-- `liveJs`        - LiveReload option to enable live JS reloading (defaults to true)
 - `liveImg`       - LiveReload option to enable live images reloading (defaults to true)
 - `dashboard`     - A boolean to prevent tiny-lr from configuring a default
   "home" route. Only used with the CLI (default: false)