Fix User#on_team?
fix TeamsController#show
clean up Team model duplication and fix grouping

- Remove duplicate association declarations
- Remove duplicate method declarations
- Remove duplicate mount_uploader
- Remove duplicate callbacks
- Remove duplicate validations
- Group associations
- Group callbacks
- Group validations
Merge pull request #261 from jakegavin/welcome-email-bug

Bounty #455 - Fix User#on_team?
Merge pull request #262 from codebender/team_model_cleanup

clean up Team model duplication and fix grouping - Bounty 462
Merge pull request #263 from jakegavin/fix-missing-opportunity

Bounty #459 - Fix