Allow currency to be set in specs via env settings

Defaults to USD.

Zuora rejects requests if supplied currency is inactive on an account. 
This will allow contributors to set currency according to their tenants.
Remove whitespace in specs
Update spec to pass in PST < timezone <= PST + 1.day
Merge pull request #13 from nvd/feature/update_specs

Minor updates to the specs
Bundle update
Upgrade rspec

Change specs to use expect syntax
Enforce locale to get rid of deprecation warning
Delete existing Gemfile.lock & gitignore it
Upgrade rspec dependency post 3.0.0 release
Merge pull request #16 from nvd/feature/update_dependencies

Upgrade dependencies
Changed dependencies to include Rails 4 versions.
Merge pull request #18 from sportngin/allow-rails4

Changed dependencies to include Rails 4 versions.
Fix incorrect ActiveZuora.generate_classes option.