[helpers] Fix all capture_concat templates to be equal in tests
[WIP] Added a cache parser for #821 with a default now to Plain.
Added Cache Parser Strategy. Fix #821

Now different than before the we store data as plain text, otherwise
we bundle also the marshal serializer or you can simply provide yours.

Example:

    Padrino.cache = Padrino::Cache::File.new(...)
    Padrino.cache.parser # => Padrino::Cache::Parser:Plain
    Padrino.cache.parser = :marshal

Or you can write your own:

    require 'oj'
    module PadrinoJSON
      def self.encode(code)
        Oj.dump(code)
      end

      def self.decode(code)
        Oj.load(code)
      end
    end

Finally you can load your strategy:

    Padrino.cache.parser = PadrinoJSON

Or if you prefer do something on the fight you can:

    Padrino.cache.parser = Module.new do
      def self.encode
      end
      def self.decode
      end
    end

//cc @padrino/core-members
[cache] Cleanup old code, add comments and fix test
Added bundler/setup to the generated Rakefile.

In that way we are sure to keep-up the correct version of our gems
Use a consistent name also for minirecord.

That fixe also an issue where tasks wasn't loaded correctly
Setup correctly all tasks
Switch to slim as default engine
Reflect slim changes on tests
Merge remote-tracking branch 'upstream/master' into super-admin

* upstream/master:
  Reflect slim changes on tests
  Switch to slim as default engine
  Setup correctly all tasks
  Use a consistent name also for minirecord.
  Added bundler/setup to the generated Rakefile.
  [cache] Cleanup old code, add comments and fix test
  Added Cache Parser Strategy. Fix #821
  [WIP] Added a cache parser for #821 with a default now to Plain.
  [helpers] Fix all capture_concat templates to be equal in tests