v0.2.0

• Added support for configuring NTP servers at runtime. Thanks to @ConnorRigby
  for sending a PR for this
• Added Nerves.Time.restart_ntpd/0 for users who know external information
  about good times to bounce the NTP daemon so that it syncs more quickly
• Fixed naming of is_synchronized/0 to be synchronized?/0. Thanks to
  @brodeuralexis for catching my slip.