Merge pull request #137 from jamesls/issue-136

lstrip values before checking for json values
Pin botocore/bcdoc version to match minor versions
Bumping version to 0.12.0
Merge branch 'release-0.12.0' into develop

* release-0.12.0:
  Bumping version to 0.12.0
Added Amazon ElastiCache to list of services.
Refactor clidriver/argparser for easier customization

This commit refactors the clidriver/argparser for easier
extension for plugins.  As a result, some of the functionality
in core was moved to extensions.

The main change was to allow each level of command/operation/args
to be represented as a table that is sent out as a signal.  This
allows extensions to add new commands/operations/arguments by
modifying the table.

I've also made a stab at integration tests to ensure I haven't
forgotten a feature that was previously supported.  These integration
tests actually run the `aws` command to ensure end to end testing.