0.16.1

Fixes

• Fix ACK re-INVITE race when offer in 200 Ok (see #798)
• Prevent invalid state transition in Registerer (see #800)
• Add documentation of WebSocket Transport (see #801)
• Fix subscription bugs related to timer N (see #802)

Features

• Add support for Retry-After on REGISTER reject (see #799)

Other

• tslint is deprecated, so replace with eslint and prettier
• Remove tslib (unnecessary after update from es5 build target)
• Remove crypto-js (new update broke some environments)
• Update target to es2017
• Update module to es2015, with package.json changes to make SIP.js a proper ES module