Update announcements

Announcements.txt

@@ -140,18 +140,18 @@ Enjoy!
 Beta release
 ============
 
-Subject: [ANN] Spyder 3.0 third public beta release
+Subject: [ANN] Spyder 3.0 fourth public beta release
 
 
 Hi all,
 
 On the behalf of Spyder's development team (https://github.com/spyder-ide/spyder/graphs/contributors),
-I'm pleased to announce the third beta of our next major version: Spyder 3.0.
+I'm pleased to announce the fourth beta of our next major version: Spyder 3.0.
 
 We've been working on this version for almost two years now and as far as we know
 it's working very well. There are still several bugs to squash but we encourage all
 people who like the bleeding edge to give it a try. This beta version is released
-six months after our second one and it includes almost 600 commits!
+three weeks after our third one and it includes more than 150 commits!
 
 Spyder 3.0 comes with several interesting and exciting new features. The most
 important ones are:
@@ -181,7 +181,7 @@ https://github.com/spyder-ide/spyder/wiki/Beta-version-changelog
 You can easily install this beta if you use Anaconda by running:
 
     conda update qt pyqt
-    conda install -c spyder-ide spyder==3.0.0b3
+    conda install -c spyder-ide spyder==3.0.0b4
 
 Or you can use pip with this command: