Only build tagged commits

[geraintwhite]

We should add an option to options.json to allow building only when a tagged commit is received (to prevent excessive builds).

[geraintwhite]

We should also add regex to the branch matching so we can match tagged payloads. (/v\d+.\d+.\d+/)

[geraintwhite]

Perhaps we should use the semver library and have a query string parameter for matching semver branches.