Updated default vagrant box to Ubuntu 14.04 from Vagrant Cloud
Merge remote-tracking branch 'upstream/master'
bump requirement on berkshelf-api version for testing
Improve error message when Berksfile.lock versions not found on `berks install`.

Addresses #1221
Improves invalid cookbook/versions in Berksfile.lock with better error messages.
[CR] Consolidate error types for missing cookbook version from Berksfile.lock.
[CR] Rename InvalidLockfileCookbookVersion to MissingLockfileCookbookVersion.
[CR] Improve comment on new missing version from Berksfile.lock in Installer.
[CR] Remove use of 'lockfile' and improve Scenario descriptions.
[CR] Remove Berksfile#versions_for as no longer necessary.
[CR] Update old v2 Berksfile.lock format to v3.
Rename status_code helper in BerkshelfError to set_status_code.

This allows sub-classing errors and calling set_status_code again to set a new
status code; otherwise, after the helper call status_code is now a singleton
accessor and no longer can be used to set the status_code.
[CR] Make MissingLockfileCookbookVersion inherit from CookbookNotFound error.
Fix failing feature
Merge pull request #1217 from jossy/master

Updated default vagrant box to Ubuntu 14.04 from Vagrant Cloud