Added test for the Python version so people could understand when their bot wouldn't run. Now it won't even install :)

setup.py

@@ -29,6 +29,12 @@
 # POSSIBILITY OF SUCH DAMAGE.
 ###
 
+import sys
+
+if sys.version_info < (2, 3, 0):
+    sys.stderr.write("Supybot requires Python 2.3 or newer.\n")
+    sys.exit(-1)
+
 import glob
 import os.path