CLI fixes: Hpricot => Nokogiri, updates, styles

[rmoriz]

Hi,

this is a rather large pull request:

• removes Hpricot, switches to Nokogiri
• tweaks some styles
• bumps dependencies as far as nothing breaks
• compatibility changed to >= 1.9.3 incl. JRuby

I would also volunteer to maintain the gem on rubygems, if this is acceptable to you.

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[eitoball]

:+1:

May I merge this request? /cc @hsbt

[hsbt]

@rmoriz Thank you!

@eitoball Please do it.

[eitoball]

@rmoriz :tada: Thank you!