Add RSA keygen example using WebCrypto Api
map JWK parameters to local BigInteger
Refactor key generation to use callback
* TODO: reactive native web crypto in rsa.js:142
* TODO: generate publicExponent Uint8Array from argument E in rsa.js:148
* TODO: signing with generated web crypto key fails with "Could not find valid key packet for signing in key"
Activate web crypto api (still fails tests)
* Remove api support for safari
* Fix error handling
Fix decoding of JWK. Webcrypto works.
Fix typo
Cleanup promise error handling
Make WebCrypto optional with config.useWebCrypto
Add documentation to getWebCrypto
Refactor keygen to use promises (Work in progress)
Refactor complete public api to use promises
Refactor web worker async proxy to use promises.
Update README with documentation on promises.
Fix phantom.js web worker tests that use promises
Add high level error messages to public api.
Upadte readme to error handling
Fix tests on travis ci.
Add es6-promise polyfill to build step so users don't have to.
Use global error catch
Merge pull request #259 from openpgpjs/promises

Refactor public api to use ES6 Promises