* Add an off-by-default 'unstable' flag
* Remove explicit web framework feature names
Having forgotten that deps and features can't have the same name,
attempts to better document all the features in one place were
misplaced.
* Split up tests on Travis
`cargo test` doesn't allow `--workspace` and `--features`
simultaneously, so we're forced to test each package separately in order
to manually specify features (or in this case, test everything but
unstable)
* Update Travis Config
- Document the state of Cargo workspaces and features
- Update the benchmarks to trickle down the 'unstable' feature
