Added a note about awesome 3.4 being currently unsupported.
Fixed #3 reported by @andreascarpino.
Also, reorganized `require` list.
Two minor changes:
1. Added a tooltip for the widget.  It reports the number of Pomodoros
   completed so far.
2. Naughty preset now refers to `beautiful` settings for urgent windows.
[git] Ignore backup and HTML files.
1. Extracted all of the messages displayed to the user to a table.
   When embedding data in messages/tooltips, `string.format` is used
   instead of simple concatenation.

2. Added three signals, allowing the user to execute arbitrary Lua
   code after completion of a Pomodoro, after a break or when the
   timer is paused/restarted.
Added documentation of the variables and signals available to the user
for customization purposes.