Add Generate A UUID as a postgres til.

postgres/generate-a-uuid.md

@@ -0,0 +1,19 @@
+# Generate A UUID
+
+Postgres has support for universally unique identifiers (UUIDs) as a column
+data type via `uuid`. If you have a UUID column, you may need to generate a
+UUID.  This requires the `uuid-ossp` module. This module provides a number
+of functions for generating UUIDs including the `uuid_generate_v4()`
+function which bases the UUID entirely off random numbers.
+
+```sql
+> create extension "uuid-ossp";
+CREATE EXTENSION
+> select uuid_generate_v4();
+           uuid_generate_v4
+--------------------------------------
+ a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11
+```
+
+See the [postgres docs](http://www.postgresql.org/docs/9.4/static/uuid-ossp.html) for more
+details on UUID generation functions.