Updates api version.

[samfrench]

• This PR has a session token section for the client added in client.ex.
• This auto-generates and updates all of the other AWS services that are in this repo.
• This adds the STS service.
• The STS service needs a different content-type and accept header. This will be added at a later date when it is clearer how this is best done.

  {"Content-Type", "application/x-www-form-urlencoded; charset=utf-8"},
  {"accept", "application/json"},

[jadeallenx]

Thanks for the PR