Extract UNSAFE regex in utilities uri to reduce memory usage

[simonprev]

While benchmarking my app (using derailed), I noticed a an unusual memory usage in the Carrierwave::Utilities::Uri module. The action benchmarked is serializing 60 records each containing a field with an uploader that has 3 versions. The memory usage is not critical and this is not a huge gain in performance so merge it if you think the code respect the guideline of the repository 😄

Here is my benchmarks results:

allocated memory by gem

Before

2399180 carrierwave/lib
1470695 activesupport-4.2.0
1444700 activerecord-4.2.0

After

1708780 carrierwave/lib
1470695 activesupport-4.2.0
1444700 activerecord-4.2.0

allocated memory by file

Before

989475 /Users/simonprev/.rbenv/versions/2.2.2/.../active_support/json/encoding.rb
817070 /Users/simonprev/Code/carrierwave/lib/carrierwave/utilities/uri.rb <-- This is unusual
509070 /Users/simonprev/Code/carrierwave/lib/carrierwave/uploader/url.rb
507460 /Users/simonprev/.rbenv/versions/2.2.2/.../json/common.rb

After
989475 /Users/simonprev/.rbenv/versions/2.2.2/.../active_support/json/encoding.rb
509070 /Users/simonprev/Code/carrierwave/lib/carrierwave/uploader/url.rb
507460 /Users/simonprev/.rbenv/versions/2.2.2/.../json/common.rb
...
126670 /Users/simonprev/Code/carrierwave/lib/carrierwave/utilities/uri.rb <-- Ahh

[bensie]

Thanks!

[bensheldon]

@simonprev just wanted to send my thanks because I noticed this exact issue too when trying to track down profligate memory usage! 👍