[FEATURE] Use new Codius sandbox
Change manifest  format to use objects to represent directories
fs API implements new, lower level file access API
Remove old runtime_library (unnecessary because of Node.js in sandbox)
Passing in API to sandbox instead of handling calls in the engine
[FIX] Correctly handle new recursive structure for `files` property.
[FIX] Fixes related to retrieving fixes in subdirs.
[FIX] Handle some other cases for package.json `main` entries.
[FEATURE] Additional property for file event: `isManifest`
[SECURITY] Add an extra sanity check for hash values in the `files` tree.
[FIX] Fix runtime library modules.
[FEATURE] Add support for outgoing TCP connections. (IPv4 only)
[FEATURE] Add crypto API for getting random data.
[TASK] Use promises to make FileManager asynchronous.
[FEATURE] Change default directory for contract_filesystem to be in $HOME.

This fixes permissions issues for globally installed CLI.
[TASK] Bump version to 0.1.0.
[FEATURE] Add fs.readdir API support.

Refactor fs API module.
[FEATURE] Passing through env variables
[FEATURE] Support for IPv6 and simulating incoming connections.
[TASK] Disable removing instances logic.

The callback for runner.run now means something different - it means that the contract has finished initializing, not that it is done and no longer needed. How long to keep contract instances around is now up to the user of the engine.
[TASK] Re-enable NaCl since seccomp is not ready yet.
[FEATURE] Emit an event when a contract starts listening.
[TASK] Cleanup. Remove exit callback.
[TASK] Remove contract_instances feature.

The host will be responsible for keeping track of and reusing contract runner instances.