EMR: Update help text and examples.
1. Add helptext description, which says leaving instance-count creates one node cluster;
2. Sanitizing add-tags example
3. Edit/change example text for create-cluster and add-tags
Fixed s3 to s3 sync urlencoding pagniation bug.

Keys were not getting url decoded properly with pagination.
If one bucket exited ListObjects pagination before
the other bucket, it caused the handler that decodes the keys
to prematurely exit as well. This resulted in some keys not
getting url decoded.
Merge pull request #909 from kyleknap/sync-encoding

Fixed s3 to s3 sync url decoding pagniation bug.
EMR: Update modify-cluster-attributes error message.
EMR: Remove UnknownApplicationError

This fix removes the validation logic on application names passed in
"aws emr create-cluster --applications Name=<application name>"
EMR: Add support for --emrfs in create-cluster command.

EMR: Update AMI version used in create-cluster --emrfs example.
Merge branch 'emr' into release-1.4.3
Updated the changelog for new features.
Bumping version to 1.4.3
Merge branch 'release-1.4.3' into develop

* release-1.4.3:
  Bumping version to 1.4.3
  Updated the changelog for new features.
  EMR: Remove UnknownApplicationError
  EMR: Update modify-cluster-attributes error message.
  EMR: Update help text and examples. 1. Add helptext description, which says leaving instance-count creates one node cluster; 2. Sanitizing add-tags example 3. Edit/change example text for create-cluster and add-tags
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