`@0x/contracts-zero-ex`: `bootstrap()` de-registers itself and self-destructs once it's called.
`@0x/contracts-zero-ex`: `bootstrap()` now takes arbitrary call data, but the callee is fixed in an immutable.
`@0x/contracts-zero-ex`: `bootstrap()` caller is fixed in an immutable.
`@0x/contracts-zero-ex`: `bootstrap()` only calls a single target.
`@0x/contracts-zero-ex`: Renamed `BasicMigration` to `InitialMigration`.
`@0x/contracts-zero-ex`: `InitialMigration` is now the bootstrap target and multiplexes to the initial features.
`@0x/contracts-zero-ex`: Add `Migrate` feature and tests.
`@0x/contracts-zero-ex`: Re-organize contract locatins (remove `interfaces` folder).
