Try to lower PGSQL memory requirements on Travis
Move SHM memory settings to defaults/ in PGSQL

Now shared memory multiplier variable will be available in inventory
variables and thus, easier to modify.
Request less shared memory for PGSQL on Travis
Add option to disable SHM changes in PostgreSQL
One more try to fix PGSQL build error on Travis
Change how PostgreSQL role sets shared_buffers

By default, if 'postgresql_sysctl_shm_multiplier' is set, PostgreSQL
role modifies kernel SHMMAX value according to total system memory and
configures PostgreSQL shared_buffers according to total system memory
divied by number of clusters configured.

If 'postgresql_sysctl_shm_multiplier' is set to False, PostgreSQL role
will now configure 'shared_buffers' setting in each cluster according to
currently set SHMMAX value, substracting additional memory required for
'max_connections'.
Merge pull request #43 from drybjed/travis

Updates to PosgreSQL memory configuration