Run:
  node injoxy.js
  Uses the default config.json configuration file
  
  node injoxy.js mycfg.json
  Uses mycfg.json as the config
  
  Config files are monitored for changes and proxy restarts when this happens automatically.


Config:
  Config file must be in valid JSON format.
  
  settings:
    proxy_port: port on which the proxy listens
    bust_cache: rewrite cache headers in the response, instructing the browser not to cache anything
  patterns:
    an array of spec:
      url: url to match
      url_match: 'equals' means url must match exacly, 'includes' just looks for a substring
      content_types: an array of content types to match
      search: regex string that defines the pattern you're looking for in the response
      inject: the string to inject in the document
      inject_method: 'before', 'after', and 'replace' the search pattern
  
Technical details:
  The proxy forces connection closing on both sides by adding "Connection: close" header to
  the request and response. This is to avoid node's file limit hit.