Add Optional `elasticache_subnet_group` (cloudposse#34)

* [issue-30] Optional elasticache_subnet_group ID

Add optional variable for the Elasticache subnet group ID so we can 
create the replication group in an already existing subnet group.

* Update main.tf

Co-Authored-By: aknysh <[email protected]>

* Update variables.tf

Co-Authored-By: aknysh <[email protected]>

* Update variables.tf

Co-Authored-By: aknysh <[email protected]>

* Update main.tf

Co-Authored-By: aknysh <[email protected]>

* Address comments, update LICENSE, update descriptions, update `README`

* Update example

* Update README

Use primary_endpoint_addess if dns is not used for host output (cloud…

…posse#38)

Fixes cloudposse#37

add cloudwatch ok alarm actions (cloudposse#32)

* add cloudwatch ok alarm actions

* updating readme from makefile

feature: update readme yaml and rebuild readme md (cloudposse#29)

Input variable for replication_group_id (cloudposse#28)

* adding an input variable for replication_group_id

* fix formatting

* updating docs

normalize disable method (cloudposse#27)

* normalize disable method

switch variable default to empty string, switch enable bool to check length of zone_id variable

* regenerate readme

Fix bug with dns zone (cloudposse#25)

Support Redis Parameters (cloudposse#24)

* Paramatrise redis

* Update label version

* Update label version

* Update example

* Fix example

Signed-off-by: Igor Rodionov <[email protected]>

* Update variables.tf

* Update terraform.md

* Update README.md

Add auth_token argument (cloudposse#23)

* add auth token

* fmt

* update readme properly

* add auth token generation to readme

Regenerate README.md (cloudposse#18)