TEMP: Trying to add markers with hover-ability.  No luck
Reverting last attempt (using markers).
TEMP: setting up ace.dart locally and testing linking
Resolved conflicts
Hovering events are working.  Temporary implementation of markers
Cleaned up
Merge branch 'master' of https://github.com/dart-lang/spark into umop-hyperlink-hover_hack
Constraining ace to next version
Setup bottom-border marker for underline-like behavior.  Also, turning mouse cursor to pointer when ACCEL'ing over an identifier.
Review fix
Rename class Diff => TreeDiff
Add git diff.
cleanup.
Add diff api to scm.
More work on git diff.
remove debug string.
Rename exception names.
Add SparkErrorMessages class.
Don't show raw exception messages.
Improvements in spark exception class.