Merge pull request #9 from BakedSoftware/master

Added support for Marketplace
Update .travis.yml to include merchant account ID
Add development environment
Transaction integration test amounts to prevent txs from being rejected as duplicates
Update .travis.yml
Add offset to transaction tests to prevent duplicates from being rejected
Merge branch 'release/0.3.0' into develop
Merge remote-tracking branch 'upstream/master' into develop
Version bump
Merge branch 'release/0.3.1'