RecordRTC possibilities of failures added

When saving recorded audio/video stream to disk, RecordRTC will fail if:

1. You're using chrome incognito mode
2. RecordRTC created duplicate temporary file
3. the requesting scheme is none of the following: http, https, chrome,
extension's, or file (only works with --allow-file-access-from-files)
4. the browser cannot create/initialize the metadata database for the
API under the profile directory