Fix unicode error in py2.7 for example plugin

Strings should now be passed to the plugins as unicode values in py2.7
so we have to make sure that we don't convert those into ascii by using
python str instead of u'' strings.

doc/example-plugins/canary.py

@@ -1,3 +1,6 @@
+from __future__ import unicode_literals
+# don't convert to ascii in py2.7 when creating string to return
+
 import time
 outputs = []
 

doc/example-plugins/counter.py

@@ -1,3 +1,6 @@
+from __future__ import unicode_literals
+# don't convert to ascii in py2.7 when creating string to return
+
 import time
 crontable = []
 outputs = []

doc/example-plugins/repeat.py

@@ -1,3 +1,6 @@
+from __future__ import unicode_literals
+# don't convert to ascii in py2.7 when creating string to return
+
 crontable = []
 outputs = []
 

doc/example-plugins/todo.py

@@ -1,4 +1,7 @@
 from __future__ import print_function
+from __future__ import unicode_literals
+# don't convert to ascii in py2.7 when creating string to return
+
 import os
 import pickle