[api test] Added `.meta()`, `.anyMeta()` and `.allMeta()` reactors for working with new `meta` property on data events for working with more structured data.
[doc] Added documentation about new `meta` for more structured data.
[api test] Ensure that `.hasMeta()`, `.anyMeta()` and `.allMeta()` can also optionally take values for keys in `data.meta`.
[minor] Expose some additional things from `common`.
Merge pull request #40 from nodejitsu/feature-meta

Add "meta" property to event data and associated Reactors