improve online help

@@ -7,17 +7,18 @@ import getpass
 from LdapTree import LdapTree
 
 def usage():
-    print "Usage: " + sys.argv[0] + " OPTION...\n"
+    print "Usage: " + sys.argv[0] + " ARGUMENT... [OPTION]...\n"
     print "Create a tree representation of all DNs starting with a given base DN."
-    print "Only simple binds to the directory with DN and password are supported."
-    print "If no password OPTION is given the password will be asked interactive."
+    print "Supports simple and kerberos binds via GSSAPI."
+    print "If no password OPTION is given for simple binds the password will be"
+    print "asked interactive."
     print "If no outfile the given the result will be written to stdout.\n"
-    print "Required OPTIONS are:\n"
+    print "ARGUMENTS:\n"
     print "  {:30s} : {:s}".format('-H, --hosturi=URI', 'The URI to the ldap server to query in the form:')
     print "  {:30s}   {:s}".format('', 'ldap[s]://host.uri[:port]')
     print "  {:30s} : {:s}".format('-D, --binddn=DN', 'The DN to use for the LDAP bind.')
     print "  {:30s} : {:s}\n".format('-b, --basedn=DN', 'The DN to start the tree with.')
-    print "Optional OPTIONS are:\n"
+    print "OPTIONS:\n"
     print "  {:30s} : {:s}".format('-h, --help', 'Show this help page')
     print "  {:30s} : {:s}".format('-p, --password=PASSWORD', 'The password to use for the LDAP bind.')
     print "  {:30s} : {:s}".format('-o, --outfile=FILENAME', 'File to write the result to.')