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.
Merge branch 'dev' of https://github.com/pickhardt/betty into dev
Added conversion support for milliseconds, microseconds and nanoseconds.
Merge pull request #89 from trizen/dev

Conversion of units.