Basic calculation support using 'bc'
Improve time query

Decided to make the current time-query parser quicker, and shorter. With this change, here are some of the queries that can be handled now:

![Screenshot](http://i62.tinypic.com/1zd8wvo.png)
show time in both 12&24hr format

This might be just a personal preference, but I would wish to see the time in both 12hr and 24hr - or should there be a separate query for viewing the time in 12hr mode?
more flexible date query

what is the date today?
whats the date today?
whats the date?
whats date?
what date?
what today?
what is today?
what the today?

_some are gramatically wrong by design_
A more human friendly date

If one should be using `betty` to check the date, then they most likely want to see something more human-friendly as well. So, I have updated the date to something like this:
 
Fri 16 May, 2014
more flexible month query

what month
whats month
whats the month
whats the month now
what is the month now
what is the month
what is month
what month is it now
what month is it
Improve day query flexibility

what is the day of the week
what is the day of the week is it
what is the day of the week is it today
what is the day of the week today
what day of the week is today
what day of the week is it today
which day of the week is it today
which day is it
which day is it today
which day
which weekday
which weekday is it
which weekday is it today
which is the weekday today
which is the weekday now
what is the day now
etc
fix a limit in the day query

should be able to ask:

whats the day
what is the day
Added lib/units.rb -- a multi-units converter;
Simplified lib/sizes.rb -- added `-h` switch for `du`;
Added conversion support for hours.
Minor code simplification.
Add os module test scratch
Add tests for all methods in module
Merge pull request #100 from christophelec/dev

Easier platform management and added support for translation and spotify...
Merge pull request #86 from mcnemesis/patch-1

Improve time query
Merge pull request #101 from igorrKurr/os-module-test

Os module test
Fix commands module.
Merge branch 'dev' of https://github.com/pickhardt/betty into dev
Added conversion support for milliseconds, microseconds and nanoseconds.
updates tar to allow output specification