now missing dep gives nicer error and docs disambiguate as several libs

out there have same name.
Signed-off-by: Brian Coca <briancoca+dev@gmail.com>

library/monitoring/pingdom

@@ -9,7 +9,7 @@ description:
 version_added: "1.2"
 author: Justin Johns
 requirements:
-    - "pingdom python library"
+    - "This pingdom python library: https://github.com/mbabineau/pingdom-python"
 options:
     state:
         description:
@@ -66,7 +66,12 @@ EXAMPLES = '''
            state=running
 '''
 
-import pingdom
+try:
+    import pingdom
+    HAS_PINGDOM = True
+except:
+    HAS_PINGDOM = False
+
 
 
 def pause(checkid, uid, passwd, key):
@@ -105,6 +110,9 @@ def main():
         )
     )
 
+    if not HAS_PINGDOM:
+        module.fail_json(msg="Missing requried pingdom module (check docs)")
+
     checkid = module.params['checkid']
     state = module.params['state']
     uid = module.params['uid']