PATCH: fix handling of plain text release notes

[Elliot Peele <elliot rpath com>]

For text documents mime ends up being text/plain.

Elliot

diff -r b27c69867066 iw/release_notes.py
--- a/iw/release_notes.py	Mon Apr 09 14:17:40 2007 -0400
+++ b/iw/release_notes.py	Tue Apr 10 16:42:47 2007 -0400
@@ -137,7 +137,7 @@ class ReleaseNotesViewer:
 					headers = f.info()
 
 					mime = headers.getheader('Content-type')
-					if mime:
+					if mime == 'text/html':
 						self.doc.open_stream(mime)
 						self.doc.write_stream(f.read())
 					else: