MAINT: update the AUTHORS.txt file.

AUTHORS.txt

@@ -1,5 +1,6 @@
-Ilan Schnell is the main developer and maintainer of Enstaller (version 4).
+Enstaller is maintained by Enthought Ltd.
 
+The current main developer/maintainer is David Cournapeau.
 
 Historical notes:
 =================
@@ -26,5 +27,8 @@ is a clean implementation of an easy_install alternative.
 In August, 2009 the first production version of the new Enstaller v4.0 which
 uses egginst and new implementation of enpkg was released.
 
+In the first half of 2014, the implementation has been significantly cleaned-up
+to make enstaller usable as a library.
+
 Many people at Enthought have provided feedback, and given suggestions,
 in particular Dave Peterson.