Adds EBS Volume support and tests for EMR Instnace Groups
```
$ make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSEMRInstanceGroup_ebsBasic'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/01/25 10:14:58 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSEMRInstanceGroup_ebsBasic -timeout 120m
=== RUN TestAccAWSEMRInstanceGroup_ebsBasic
--- PASS: TestAccAWSEMRInstanceGroup_ebsBasic (675.14s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws 675.171s
```
use us-west-2 region in tests
update test with working config
provider/aws: Update EMR contribution with passing test, polling for instance in DELETE method
remove defaulted role
document emr_cluster
rename aws_emr -> aws_emr_cluster
update docs for name change
update delete timeout/polling
rename emr taskgroup to emr instance group
default instance group count to 0, down from 60
update to ref emr_cluster, emr_instance_group
more cleanups for instance groups; need to read and update
add read, delete method for instance groups
refactor the read method to seperate out the fetching of the specific group
more refactoring for finding instance groups
update emr instance group docs
err check on reading HTTP. Dont' return the error, just log it
refactor the create method to catch optionals
additional cleanups, added a read method
update test to be non-master-only
wrap up the READ method for clusters
poll for instance group to be running after a modification
patch up a possible deref
provider/aws: EMR cleanups
fix test naming
remove outdated docs
randomize emr_profile names
Jake Champlin