Add notes for 'monotime' Gem, which may well prove useful in future.

/~https://github.com/Freaky/monotime looks quite useful for measurements and running timings, when we get around to doing profiling. This commit adds `XXX:` notes to both the Gemspec and the Gem-installation-list builder as reminders to think about this later.

[Pinging #16]

44 tests, 63 assertions, 0 failures, 0 errors, 0 skips
Coverage: 466 / 466 LOC (100.0%) covered.
RuboCop: 7 files inspected, no offenses detected
Flay: Total score 0
Flog: Total 161.3; method average 4.7; max 9.8 (CryptIdent::SignUp#create_result)
Reek: 0 total warnings
Inch: Nothing to suggest

crypt_ident.gemspec

@@ -57,6 +57,9 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'minitest-matchers' #, '1.4.1'
   spec.add_development_dependency 'minitest-reporters' #, '1.3.5'
   spec.add_development_dependency 'minitest-tagz' #, '1.6.0'
+  # XXX: Great idea; useful; but we've found a way to work around what we were
+  # looking to use this Gem to help with.
+  # spec.add_development_dependency 'monotime' #, '0.6.1'
   spec.add_development_dependency 'pry-byebug' #, '3.6.0'
   spec.add_development_dependency 'pry-doc' #, '0.13.5'
   spec.add_development_dependency 'reek' #, '5.2.0'

scripts/build-gem-list.rb

@@ -63,6 +63,9 @@ def gem_strings(list)
   'minitest-reporters:1.3.5',
   'minitest-tagz:1.6.0',
   'minitest:5.11.3',
+  # XXX: A useful Gem, but not needed for what we were considering using it for
+  # immediately.
+  # 'monotime:0.6.1',
   'pry-byebug:3.6.0',
   'pry-doc:0.13.5',
   'rake:12.3.1',
@@ -74,4 +77,13 @@ def gem_strings(list)
   'yard:0.9.16'
 ]
 
+# pp [:file, __FILE__]
+# gemspec = Gem::Specification.load(File.expand_path('../../crypt_ident.gemspec',
+#       __FILE__))
+# pp [:gemspec, gemspec.dependencies.map(&:to_s)]
+# list2 = gemspec.dependencies.map do |dep|
+#   [dep.name, dep.to_spec.version.to_s].join(':')
+# end
+
+# require 'pry-byebug'; binding.pry
 puts gem_strings(list).join(' ')