Suggest texts based on history

History has text and count. Frequently entered texts are suggested
first in Omnibox.
Modulize History and add specs for unit tests
Remove underscore dependency
Merge branch 'suggest_previous_timers'
Use parseFloat() instead of parseInt() for time

This will allow people to input things like 3.5h. I think the main
use case is hour input.
Something has been changed for notification

WebkitNotification object does not seem to have close() function any
more. I would keep the same code and add just checking whether
event has close() function.
Merge branch 'fix_ui_issues'
Add History.findByTime() and refactor based on that
Rename variables
Show option to change history suggestion type
Polish Options page a bit
Polish how to show suggestion

Now when start typing, it changes default suggestion with typed text.
If a user enters the text, Chrome seems to remember the final text and
show it when she enters 'tm<tab>'.

The plan is to use default suggestion to show the parsing result.
Bump up to 0.4.0
Merge branch 'add_time_to_history'
Add helpful images