indent process_id based on hierarchy and popup timeline annotaations on mouseover.
updated README based on viewer enhancement.
fixed position of annotation popup based on window scrolling, with some formatting nit.
fixed sort order of spans in view.
Merge pull request #35 from iwasakims/enhance-viewer

Showing span hierarchy and timeline annotations in viewer.  Adds timing (in milliseconds output per span) and a red dot shows up when there is an annotation to view.