Rename aws_db_instance.subnet_group_name to db_subnet_group_name
Store aws_db_instance.password in tfstate, change to AttrTypeCreate
terraform: require the prefix match with a "." in Diff.Instances
providers/aws: set the dns_name on create [GH-393]
providers/aws: convert autoscaling group to helper/schema
providers/aws: launch configuration in helper/schema
fmt
helper/schema: don't say that a set is computed if it exists
helper/schema: set the field to empty if it is a list and computed
Update CHANGELOG
providers/aws: support non-destructive update of desired_capacity for
ASG
Update CHANGELOG
providers/aws: resource ELB listeners [GH-314]
providers/aws: main_route_table_id attribute for VPC [GH-193]
providers/aws: security group VPC ID can be computed in a default VPC
providers/aws: forcenew on SGs for now [GH-299]
helper/schema: sets must be treated atomically within ResourceData

This fixes a seemingly minor issue (GH-255) around plans showing changes
when in fact there are none. But in reality this turned out to uncover a
really terrible bug.

The effect of what was happening was that multiple items in a set were
being merged. Now, they were being merged in the right order, so if you
didn't have rich types (lists in a set) then you never saw the effect
since the later value would overwrite the earlier. But with lists (such
as in security groups), you would end up with the lists merging. So, if
you had one ingress rule with CIDR blocks and one with SGs, then after
the merge both ingress rules would have BOTH CIDR and SGs, resulting in
an incorrect plan (GH-255).

This fixes the issue by introducing a `getSourceExact` bitflag to the
ResourceData source. When this is set, ALL data must come from this
level, instead of merging lower levels. In the case of sets and diffs,
this is exactly what you want: "Get me the set 'foo' from the config and
the config ONLY (not the state or diff or w/e)".

Andddddd its fixed.

GH-255
fmt
providers/aws: properly report errors if DB instance destroy fails
[GH-310]
Update CHANGELOG