- Adds docs to sidebar
- Changes `volume` to `volume_name` in volume snapshot
- Fixes tests
- Changes `parent_volume_bootable` to boolean, and converts to string for API
```
$ make testacc TEST=./builtin/providers/opc TESTARGS="-run=TestAccOPCStorageVolumeSnapshot_basic"
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/04/06 12:26:59 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/opc -v -run=TestAccOPCStorageVolumeSnapshot_basic -timeout 120m
=== RUN TestAccOPCStorageVolumeSnapshot_basic
--- PASS: TestAccOPCStorageVolumeSnapshot_basic (24.45s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/opc 24.476s
```