Implemented caching for API calls

Introduced new decorators:
 * response - responsible for parameters processing
 * cached - get/set to cache
Removed all search functionality in API methods.
Fixed logging.

implements bp cache-api-methods

Change-Id: I91d36424a36442a09591c140e9f22401139b7415

stackalytics/processor/utils.py

@@ -42,7 +42,7 @@ def date_to_timestamp(d):
 def date_to_timestamp_ext(d):
     try:
         return date_to_timestamp(d)
-    except ValueError:
+    except (ValueError, TypeError):
         return int(d)
 
 
@@ -72,6 +72,10 @@ def timestamp_to_day(timestamp):
     return timestamp // (24 * 3600)
 
 
+def round_timestamp_to_day(timestamp):
+    return (int(timestamp) // (24 * 3600)) * (24 * 3600)
+
+
 def check_email_validity(email):
     if email:
         return re.match(r'[\w\d_\.-]+@([\w\d_\.-]+\.)+[\w]+', email)