update to dropbox 2.10.3
Merge pull request #14 from lonnen/update-2-10-3

update to dropbox 2.10.3
Parameterize the dropbox version

... and update to 2.10.28
Fix rspec syntax error
Bump cardboard gem dependencies

These updates are required to get specs working properly with
e.g. `let(:params) ...` blocks.
Merge pull request #15 from boxen/parameterize-version

Parameterize the dropbox version
Merge upstream/master