[lib] Use jsonld.js request extension.
[lib] Remove unused requires.
[examples] Use package version for examples.
[lib] Use default keySize for createKeyPair().
[lib] Use constant context URLs, contexts, and frames.

Switch from functions creating new contexts to static constants:

CONTEXT_V1_URL - v1 payswarm context URL
CONTEXT_URL - current payswarm context URL
CONTEXTS - context objects indexed by URL
CONTEXT - current context object
FRAMES - frames indexed by 'Asset', 'License', and 'Listing'
[examples] Add more debug output.
[package] Update dependency versions.
[docs] Use AUTHORS file for contributors.
[lib] Update use of the jsonld.request function.

- Update jsonld.use call.
- Remove unused 'request' require.
- Add options to GET and POST functions.
- Use jsonld.request for default POST implementation.
- Update docs.
[lib] Add 'use strict'.
[lib] Fix function call typos in untested code.
[lib] Add FIXME comment.
[docs] Reformat README and add 'Authors' section.
[docs] Clean up license text.

- Add LICENSE file.
- Add License section to README.
- Update code license blocks.
[docs] Switch link location.
[package] Ignore cruft and config files.
[package] Release 0.10.0.