Replace interpolated interpolation with cleaner method

[dillonwelch]

In micro-benchmarking, this change performs within margin of error of
the existing code but saves a string allocation each time the method is
called (assuming the quote strings in the old code were frozen).

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update
                your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"

  gem "benchmark-ips"
end

def allocate_count
  GC.disable
  before = ObjectSpace.count_objects
  yield
  after = ObjectSpace.count_objects
  after.each { |k,v| after[k] = v - before[k] }
  after[:T_HASH] -= 1 # probe effect - we created the before hash.
  GC.enable
  result = after.reject { |k,v| v == 0 }
  GC.start
  result
end

interpolated = "hi"

  puts "'"' + interpolated + '"'"
  puts allocate_count { 1000.times { '"' + interpolated + '"' } }
  puts "%(\"\#{interpolated}\")"
  puts allocate_count { 1000.times { %("#{interpolated}") } }
  puts "\"\#{interpolated}\""
  puts allocate_count { 1000.times { "\"#{interpolated}\"" } }

Benchmark.ips do |x|
  x.report("'"' + interpolated + '"'") { '"' + interpolated + '"' }
  x.report("%(\"\#{interpolated}\")")  { %("#{interpolated}") }
  x.report("\"\#{interpolated}\"")     { "\"#{interpolated}\"" }
  x.compare!
end

' + interpolated + '
{:FREE=>-1892, :T_STRING=>2052}
%("#{interpolated}")
{:FREE=>-1001, :T_STRING=>1000}
"#{interpolated}"
{:FREE=>-1001, :T_STRING=>1000}
Warming up --------------------------------------
' + interpolated + '    81.706k i/100ms
%("#{interpolated}")   106.128k i/100ms
   "#{interpolated}"   137.855k i/100ms
Calculating -------------------------------------
' + interpolated + '      3.892M (±23.2%) i/s -     17.975M in   5.007068s
%("#{interpolated}")      3.722M (±17.3%) i/s -     17.830M in   5.022549s
   "#{interpolated}"      3.725M (±15.0%) i/s -     18.059M in   5.023493s

Comparison:
' + interpolated + ':  3892392.6 i/s
   "#{interpolated}":  3725385.8 i/s - same-ish: difference falls within error
%("#{interpolated}"):  3722401.7 i/s - same-ish: difference falls within error

results of benchmark.rb

                                         Haml |     ERB |  Erubis |
-------------------------------------------------------------------
Cached                                  0.094 |   0.083 |   0.073 |
ActionView                             16.937 |  11.760 |         |
ActionView with deep partials          38.459 |  40.428 |         |

compared to current master

                                         Haml |     ERB |  Erubis |
-------------------------------------------------------------------
Cached                                  0.174 |   0.420 |   0.224 |
ActionView                             21.360 |  11.631 |         |
ActionView with deep partials          43.563 |  39.238 |         |

[amatsuda]

@oniofchaos Could you squash your commits, resolve the conflict in CHANGELOG, then push -f please?

[dillonwelch]

@amatsuda done!

[amatsuda]

Thanks!