added extra field in the memberships table for joining projects that may or may not be needed. Added action to join project in the project controller, that method delegates to a model method in the project model. Created link helper in project helper for joining and leaving projectrs. Also added attr accessible in membership model. No tests for this functionality yet, however all tests are still passing.
moved methods around, accomplished nothing since last commit. Still no tests. Will complete soon.
added project controller method that allows user to leave project so long as they are not the creator of the project. Also created rspec tests for joining a project.