Improve readability and fix capistrano wiki links

[brki]

• Make long sentences easier to understand by breaking them into shorter sentences.
• Consistently use : before anounced examples.
• Make overall document style more consistent.
• Minor grammar fixes.
• Fix links to capistrano wiki

[stefanooldeman]

I've merged your changes into my fork. have a look: https://github.com/stefanooldeman/capistrano-handbook/commits/master