Handle recursive shapes in shorthand parser
Document recursive shapes

For now we just document one level of recursion and then
note that it's recursive.  I've added some basic unit tests
that at least verify the doc generation process doesn't get stuck
in an infinite loop.
Expand '~' in credentials filename

Otherwise we try to write a file '~/.aws/credentials'
which is not what we want.  Originally reported on the
AWS CLI forums.
Add configure bugfix to the changelog
Add dynamodb feature to the changelog
Bumping version to 1.5.1
Merge branch 'release-1.5.1' into develop

* release-1.5.1:
  Bumping version to 1.5.1
  Add dynamodb feature to the changelog
  Add configure bugfix to the changelog
  Expand '~' in credentials filename
  Document recursive shapes
  Handle recursive shapes in shorthand parser