This commit removes the need to calculate the time remaining in a
session and instead introduces a countdown counter which decrements at
each one second 'tick'. This stabilizes the interface where it appeared
that he timer was randomly pausing or skipping time.
A summary of changes made in this commit includes:
- Updated the command line flags so that they are easier to remember.
- The work, short break and long break session times are now parsed and
converted to type float64. These times represent the total amount of
seconds.
- Removal of timer and finish from Pominal.
- The method that calculates the time remaining is removed.
- A countdown counter is added to the Pominal type.
- Updated alert message for the desktop notification.
- Simplified the Run method by moving the logic to chosse the next session
in a separate method.
