Add shorthand for --include-environments flag, "-i".

lib/arkana/models/arguments.rb

@@ -30,7 +30,7 @@ def initialize
       opt.on("-f", "--flavor FrostedFlakes", "Flavors are useful, for instance, when generating secrets for white-label projects. See the README for more information") do |o|
         @flavor = o
       end
-      opt.on("--include-environments debug,release", "Optionally pass the environments that you want Arkana to generate secrets for. Useful if you only want to build a certain environment, e.g. just Debug in local machines, while only building Staging and Release in CI. Separate the keys using a comma, without spaces. When ommitted, Arkana generate secrets for all environments.") do |o|
+      opt.on("-i", "--include-environments debug,release", "Optionally pass the environments that you want Arkana to generate secrets for. Useful if you only want to build a certain environment, e.g. just Debug in local machines, while only building Staging and Release in CI. Separate the keys using a comma, without spaces. When ommitted, Arkana generate secrets for all environments.") do |o|
         @include_environments = o.split(",")
       end
     end.parse!