Update Spring, Spring Security, Gson dependencies

- Update Spring 4.0.2 to 4.0.6
  - [4.0.2 --> 4.0.3](https://jira.spring.io/browse/SPR/fixforversion/14307)
  - [4.0.3 --> 4.0.4](https://jira.spring.io/browse/SPR/fixforversion/14370)
  - [4.0.4 --> 4.0.5](https://jira.spring.io/browse/SPR/fixforversion/14502)
  - [4.0.5 --> 4.0.6](https://jira.spring.io/browse/SPR/fixforversion/14629)
- Update Spring Security 3.2.1 to 3.2.5
  - [3.2.1 --> 3.2.2](https://jira.spring.io/browse/SEC/fixforversion/14356)
  - [3.2.2 --> 3.2.3](https://jira.spring.io/browse/SEC/fixforversion/14399)
  - [3.2.3 --> 3.2.4](https://jira.spring.io/browse/SEC/fixforversion/14496)
  - [3.2.4 --> 3.2.5](https://jira.spring.io/browse/SEC/fixforversion/14531)
- Update Gson 2.2.2 to 2.2.4
  - [2.2.2 --> 2.2.4](https://sites.google.com/site/gson/gson-roadmap)
- Code fixes due to dependency updates