EMR: Add support for --emrfs in create-cluster command.

EMR: Update AMI version used in create-cluster --emrfs example.
EMR: Use region from profile for when global argument is not passed when building EMR applications
Merge branch 'emr' into release-1.4.4
Updated changelog for new feature.
Bumping version to 1.4.4
Merge branch 'release-1.4.4' into develop

* release-1.4.4:
  Bumping version to 1.4.4
  Updated changelog for new feature.
  EMR: Use region from profile for when global argument is not passed when building EMR applications
  EMR: Add support for --emrfs in create-cluster command.
Add test coverage to credentials file

Cleaned up the code a bit before making feature changes.
The configure command writes out cred vars to shared credentials file

Fixes #847.  The change is implemented as specified in the issue:

* Anytime you set credential variables (access_key/secret_key/session_token)
  using the `configure` command or the `configure set` command, the
  values are always written to `~/.aws/credentials`.
* Getting access_key/secret_key/session_token will look in the
  shared credentials file first before looking in the CLI config file.

This does *not* do anything with automatically migrating over to the
shared credentials file, that is, if you have credentials in the CLI
config file and you run `aws configure` and hit enter 4 times, we
will not write out values to the shared credentials file because
there are no new values to write out.
Incorporate review feedback.
Add issue #847 to the changelog
Merge branch 'creds-file-default' into develop

* creds-file-default:
  Add issue #847 to the changelog
  Incorporate review feedback.
  The configure command writes out cred vars to shared credentials file
  Add test coverage to credentials file
Errors and warnings are printed to stderr.
Cleaned up ``print_thread`` code.
Merge pull request #919 from kyleknap/errors-to-stderr

Errors and warnings are printed to stderr.
Added a ``--only-show-errors`` argument.

For s3 commands, this argument supresses output written to stdout while
allowing errors and warnings to be displayed via stderr.
Improved s3 output testing.
Updated changelog with latest feature.
Merge pull request #921 from kyleknap/show-error

Added a ``--only-show-errors`` argument.
Added the ability to stream data using ``cp``.

This feature enables users to stream from stdin to s3 or from s3 to stdout.
Streaming large files is both multithreaded and uses multipart transfers.
The streaming feature is limited to single file ``cp`` commands.
Cut down memory usage to mutipart upload a stream.