add module usage info to docs

jc/parsers/crontab.py

@@ -1,9 +1,14 @@
 """jc - JSON CLI output utility crontab command and file Parser
 
-Usage:
+Usage (cli):
 
     specify --crontab as the first argument if the piped input is coming from crontab -l or a crontab file
 
+Usage (module):
+
+    import jc.parsers.crontab
+    result = jc.parsers.crontab.parse(crontab_output)
+
 Compatibility:
 
     'linux', 'darwin', 'aix', 'freebsd'