6.2.0

• Enabled application extension API only.
  @lightsprint09
• Disabled a flaky redirect test and adding the known issue with redirects to the README.
  @jeffctown
  #301
• Added isMethodHEAD() to the Swift helpers.
  @Simon-Kaz
  #294
• Fixed issue with not preserving correct headers when following 3xx
  redirects.
  @sberrevoets