Add exercises for setTimeout and setInterval
Hard wrap lines at 80 chars in settimeout_and_setinterval readme
Add description to README for setTimeout and setInterval
Remove unnecessary challenges

- Don't focus on how to log things to the console (keep focus on topic
  at hand)
- Give a helpful name for a variable
Define named function for use in timer to show flexibility
Do not wait as long for session timeout

Because who wants to wait 2 minutes to see if it works
Use better variable name s/index/timesCounted
Merge pull request #5 from codeunion/settimeout-setinterval

Exercises and description for setTimeout and setInterval