Minor updates, adding EARLS_HOSTNAME

[remagio]

• views/index.hbs, corrects a misspelling of maxiumum-scale with
  maximum-scale. A fix for mobiles.
• earls.js, it binds with all local IPs using app.listen but setting
  only default port. Added an EARLS_HOSTNAME with defaults = "". It binds
  anyway with all local IPs.
• earls.js, changed PORT with EARLS_PORT for compatibility: PORT and
  HOSTNAME are commonly used on Unix, avoiding conflicts.
• earls.js, current release use HTTPS for tweets & accounts but HTTP
  for avatar (profile_image_url). Using the profile_image_url_https it
  solves most crash/errors when earls publish lots of URLs and avatars.
• README.md, updates for descriptions of EARLS_PORT and EARLS_HOSTNAME.