Interpolate URLs using a string rather than a regex

[stretchkennedy]

Several other users have had problems with the speed of Paperclip::Interpolations.interpolate or with model.attachment.url (#557, #909). gsub with a string is significantly faster than gsub with a regex, and changing to a string also prevents users from creating interpolations with ? wildcards in them.

See:

irb(main):001:0> require 'benchmark'
=> true
irb(main):002:0> puts Benchmark.measure{100_000.times{":foo/:bar".gsub(/:#{:bar}/, 'BAR')}}
  2.290000   0.030000   2.320000 (  2.425150)
=> nil
irb(main):003:0> puts Benchmark.measure{100_000.times{":foo/:bar".gsub(":#{:bar}", 'BAR')}}
  0.860000   0.010000   0.870000 (  1.001322)
=> nil

[houndci-bot]

Unused block argument - match. You can omit the argument if you don't care about it.

[dgynn]

You might be interested in #1888 which also does gsub against a string token as well as some other performance optimizations. I've tried you test case with a :foo? interpolator and that works too.

[stretchkennedy]

I totally missed #1888. I'm fine with closing this PR, but it would be great to get the test case into the other one.

[jyurek]

Ok, then. Seeing as this is a subset of what #1888 provides, I'll close this. Thanks for submitting it, though, @stretchkennedy.