Bugfixes, features, and refactors (Oh my)

[Brandon-Schefstad]

BugFixes:

• Removed delay caused by setInterval when starting/stopping the timer.
• Removed audio delay on button press.
• Timer defaults to 25 minutes on page load

Features:

• Start/Stop button changes color on activation
• Start/Stop button plays sound on press
• Tag buttons play sounds when clicked

Refactors:

• Split handleTimer into separate functions since it was rather long as a function.