Add option to disable URL normalization

[ziaulrehman40]

Fixes #123

[fschwahn]

Looks good to me.

One other possibility to achieve this would be to let users define the clean_url-mechanism, by moving the clean_url-logic to a lambda which is changeable, eg. Shortener.clean_url = ->(url) { url }. Not sure this flexibility is even desired here though. @jpmcgrath @olleolleolle thoughts?

[ziaulrehman40]

@fschwahn Sounds good, but i guess we can do this in another iteration. For now this should be enough. Because cleaning URL is still possible on the app logic end. So we should be good.

[olleolleolle]

I like the functionality!

I added GitHub Suggestions about spec it style.

[ziaulrehman40]

@olleolleolle Thanks for merging, but as it has got in repo's readme, this should be released as well otherwise users could be trying using the option while it is not yet released.

[jpmcgrath]

Released as v0.8.2: https://rubygems.org/gems/shortener/versions/0.8.2