Add commit range to the CLI

This adds 4th and 5th optional CLI parameters that specifies the first
and last SHA commit to generate stats between.
The generator and repo classes were changed to take these as
initialisation parameters.
It would be nice to have the CLI take individual named optional
parameters, so that only first or last commit could be given and
without having to give the language.
[closes #11] using highline to parse command line options
Bump to 1.0.6
Force encoding to utf-8 for other characters
Merge pull request #17 from riveramj/gibberish-translator

Thanks for this :)
[closes #16] days without commits are not ommited on date charts anymore
tests fixed
Merge pull request #16 from tomgi/empty_days_on_charts
Bump to 1.0.7
Added german localization.
Merge pull request #19 from dbck/german_localization

Added german localization.
Ignore rvm or rbenv related dotfiles.
Changed hightlight gem to thor.
Modified the cli to base on thor gem.
Adjusted readme with some usage examples.
Merge pull request #21 from dbck/ignore_rvm_or_rbenv_related_files

Ignore rvm or rbenv related dotfiles.
Merge pull request #22 from dbck/using_thor_as_cli

Using thor as cli
Bump to 1.0.8
minimum dependencies requirements
Bump to 1.0.9