Upgrade mincer, less and bootstrap
Fix Preroll support

* StreamEdit: Add preroll field to the edit UI
* Preroller: Take a URI as input instead of an opts hash
* Preroller: Take separate socket and writer options to pump
* Shoutcast: Move creation of the Icecast writer earlier in the connection
  flow so that preroll gets counted in our bytes for metadata
* Slave SocketSource: add getStreamKey() function