Write CHANGELOG for v0.10.0

CHANGELOG.md

+# [v0.10.0](https://github.com/dtan4/terraforming/releases/tag/v0.10.0) (2016-08-24)
+
+## Resource
+
+- AWS NAT Gateway [#240](https://github.com/dtan4/terraforming/pull/240) (thanks @brianknight10)
+
+## Fixed / Updated
+
+- Use the latest Oj (2.17.x [#257](https://github.com/dtan4/terraforming/pull/257)
+- Use the latest aws-sdk (2.5.x) [#256](https://github.com/dtan4/terraforming/pull/256)
+- Attach AWS-scoped IAM policy attachments [#251](https://github.com/dtan4/terraforming/pull/251) (thanks @raylu)
+- Fix LaunchConfiguration tf result when associate_public_ip_address [#250](https://github.com/dtan4/terraforming/pull/250) (thanks @gotyoooo)
+- Paginate IAM Group Membership [#248](https://github.com/dtan4/terraforming/pull/248) (thanks @raylu)
+- Add option to use AWS bundled CA certificate [#246](https://github.com/dtan4/terraforming/pull/246) (thanks @mattgartman)
+- Fix network_interface naming in EIP [#243](https://github.com/dtan4/terraforming/pull/243)
+- Fix name of "iampa" subcommand in CLI help output [#237](https://github.com/dtan4/terraforming/pull/237) (thanks @jimmycuadra)
+- Paginate all resources [#236](https://github.com/dtan4/terraforming/pull/236) (thanks @philsnow)
+
+OpsWorks support was omitted at v0.10.0 due to lack of tests. See [#264](https://github.com/dtan4/terraforming/pull/264) in detail.
+
+## Others
+
+- Introduce [RuboCop])(https://github.com/bbatsov/rubocop) and [SideCI](https://sideci.com/) to check coding style automatically [#242](https://github.com/dtan4/terraforming/pull/242)
+
 # [v0.9.1](https://github.com/dtan4/terraforming/releases/tag/v0.9.1) (2016-06-17)
 
 ## Fixed / Updated