<h1>The DirtyGutter plugin</h1>
Written by Shlomy Reinstein, August 2009.<br>
The DirtyGutter plugin marks dirty lines (lines modified since last save) in the
Gutter area. The dirty line information is provided by a so-called "Dirty line
provider", which is an extensible service. Two built-in providers are included:
<li>"Simple" - marks any modified lines with a colored marker by tracking buffer
<li>"Diff" - uses a "diff" algorithm to calculate dirty lines for each multi-
line content change. Uses a simple algorithm for marking single-line changes.
Marks the changes according to their types (change/insertion/removal).