message: Revise math tutorial
  Fix bug in section tags
diff: * <a href="#The-MathSender-Component_Write-and-Run-Unit-Tests_Set-Up-the-Unit-Test-Environment">4.5.1. Set Up the Unit Test Environment</a>
  * <a href="#The-MathSender-Component_Write-and-Run-Unit-Tests_Write-and-Run-One-Test">4.5.2. Write and Run One Test</a>
  * <a href="#The-MathSender-Component_Write-and-Run-Unit-Tests_Write-and-Run-More-Tests">4.5.3. Write and Run More Tests</a>
  - * <a href="#The-MathSender-Component_Write-and-Run-Unit-Tests_Exercise:-Random-Testing">4.5.4. Exercise: Random Testing</a>
  + * <a href="#The-MathSender-Component_Write-and-Run-Unit-Tests_Exercise-Random-Testing">4.5.4. Exercise: Random Testing</a>
  * <a href="#The-MathSender-Component_Reference-Implementation">4.6. Reference Implementation</a>
  <a name="Introduction"></a>
  @@ -1066,7 +1066,7 @@ Again you can try altering something in the component code
  to see what effect it has on the test output.
  <a name="math-sender_exercise"></a>
  -<a name="The-MathSender-Component_Write-and-Run-Unit-Tests_Exercise:-Random-Testing"></a>
  +<a name="The-MathSender-Component_Write-and-Run-Unit-Tests_Exercise-Random-Testing"></a>
  ### 4.5.4. Exercise: Random Testing
  F Prime provides a module called `STest`
  