There is no logout button in the Community version (it was later implemented for the Standard edition).
Unfortunately - you have only one option in case you don't want to clear the cookies - to force your browser to prompt you for credentials each time you open TeamPulse - this way you can choose which user to use.
You can use Firefox or Safari - they will prompt you for credentials every time by default.
For IE - use Tools -> Internet Options -> Security -> Custom Level ... -> User Authentication - Logon -> select "Prompt for username and password".
I hope this will be useful for you.
All the best,
the Telerik team