Use adapter.js

[thijstriemstra]

The webrtc adapter.js provides a shim to insulate apps from browser spec changes and prefix differences.

Now that we also use media constraints it makes sense to include this adapter, even though an extra dependency should always be avoided, if possible. Perhaps the code can be adapted/included?

Besides the cross-browser constraint support it also helps with #16 and maybe #13.

[thijstriemstra]

Perhaps core compatibility code for things like getUserMedia and MediaStream.stop() will always be part of videojs-record, but support for 'extras' like enumerateDevices (#16) or consistent constraints definitions you would need to include some or all of adapter.js (e.g. https://webrtc.github.io/adapter/adapter-latest.js).

[thijstriemstra]

adapter.js isn't necessary for videojs-record until now so I'll close this. If you have troubles with e.g. media constraints across browers, you're free to include adapter.js.