Make option name more meaningful

I just noticed a code review which suggested against the name
we are currently using and gave some good reasoning:

"Naming things "new" is always a problem (since time passes and
it's no longer new). Maybe colonize_symbol_keys? ("colonize"
sounds kind of gross though...)
https://git.io/vKIiX

The ruby19_syntax name was suggested later in the conversation.

As we have not yet released with the previous option name, it's
now or never for this change.

README.md

@@ -41,7 +41,7 @@ plain:           false,  # Use colors.
 raw:           false,  # Do not recursively format instance variables.
 sort_keys:     false,  # Do not sort hash keys.
 limit:         false,  # Limit arrays & hashes. Accepts bool or int.
-new_hash_syntax: false,  # Use Ruby 1.9 hash syntax in output.
+ruby19_syntax: false,  # Use Ruby 1.9 hash syntax in output.
 color: {
   args:       :pale,
   array:      :white,

lib/awesome_print/formatters/hash_formatter.rb

@@ -28,10 +28,10 @@ module AwesomePrint
 
         data = data.map do |key, value|
           indented do
-            if options[:new_hash_syntax] && symbol?(key)
-              new_hash_syntax(key, value, width)
+            if options[:ruby19_syntax] && symbol?(key)
+              ruby19_syntax(key, value, width)
             else
-              old_hash_syntax(key, value, width)
+              pre_ruby19_syntax(key, value, width)
             end
           end
         end
@@ -50,12 +50,12 @@ module AwesomePrint
         k.first == ':'
       end
 
-      def new_hash_syntax(k, v, width)
+      def ruby19_syntax(k, v, width)
         k[0] = ''
         align(k, width - 1) << colorize(": ", :hash) << inspector.awesome(v)
       end
 
-      def old_hash_syntax(k, v, width)
+      def pre_ruby19_syntax(k, v, width)
         align(k, width) << colorize(" => ", :hash) << inspector.awesome(v)
       end
 

lib/awesome_print/inspector.rb

@@ -21,7 +21,7 @@ module AwesomePrint
         raw:           false,  # Do not recursively format instance variables.
         sort_keys:     false,  # Do not sort hash keys.
         limit:         false,  # Limit arrays & hashes. Accepts bool or int.
-        new_hash_syntax: false,  # Use Ruby 1.9 hash syntax in output.
+        ruby19_syntax: false,  # Use Ruby 1.9 hash syntax in output.
         color: {
           args:       :pale,
           array:      :white,

spec/formats_spec.rb

@@ -276,7 +276,7 @@ EOS
     end
 
     it "new hash syntax" do
-      expect(@hash.ai(:plain => true, :new_hash_syntax => true)).to eq <<-EOS.strip
+      expect(@hash.ai(:plain => true, :ruby19_syntax => true)).to eq <<-EOS.strip
 {
     1 => {
         sym: {
@@ -328,7 +328,7 @@ EOS
     end
 
     it "colored with new hash syntax" do
-      expect(@hash.ai(:new_hash_syntax => true)).to eq <<-EOS.strip
+      expect(@hash.ai(:ruby19_syntax => true)).to eq <<-EOS.strip
 {
     1\e[0;37m => \e[0m{
         sym\e[0;37m: \e[0m{