Add support for OS X's md5 utility

This change checks for LSB's md5sum utility and OS X's md5 utility (in
that order) and uses whichever it finds.
Use 64K progress dots for wget downloads
Speed up Node.js tests by caching downloads
Speed up Node.js compilation
Speed up Python tests by caching pip downloads
Make Debian package install less verbose
Abort if no MD5 utility can be found [#56]
Allow options when creating PostgreSQL users

Before this change, PostgreSQL users were created with cleartext
passwords and no options.  This change allows you to specify options
when a PostgreSQL user is created.  It does not allow you to require a
specific option on an existing user.
Add examples for options in Postgres user creation [#47]
Switch to keyword args for Postgres user creation [#52]
Added reload() and force_reload() service functions.
Added warnings about reload/force-reload support
missing fabtools.supervisor import in require.redis
simple smoke test for redis
Fix typos in documentation [#50]
Refactor tests
Optionally include/exclude fabfiles from functional tests
Optionally keep vagrant box up after running functional tests
Rename VAGRANT_BOXES env var to FABTOOLS_TEST_BOXES
Improve user creation and modification