Merge pull request #81 from CartoDB/equalint

adding equal interval function for consistency

test/CDB_EqualIntervalBinsTest.sql

@@ -0,0 +1,5 @@
+WITH data AS (
+    SELECT array_agg(x::numeric) s FROM generate_series(1,300) x 
+        WHERE x % 5 != 0 AND x % 7 != 0
+    ) 
+SELECT round(unnest(CDB_EqualIntervalBins(s, 7)),7) FROM data

test/CDB_EqualIntervalBinsTest_expect

@@ -0,0 +1,7 @@
+43.5714286
+86.1428571
+128.7142857
+171.2857143
+213.8571429
+256.4285714
+299.0000000