Change object tokens, support bare key-values

This commit makes several changes to the proposed lexer.

First, it changes the tokens used in JavaScript objects. It was proposed
that keys be tokenised as `Str::Double` and that string values be
tokenised as `Name::Tag`. The token `Name::Label` seems a more
appropriate token for keys while `Str::Double` should be used for
string values.

Second, it remoeves the tokenisation of escape sequences inside object
keys. While this is correct insofar as the keys are merely strings, it
fits awkwardly with the tokenisation of keys with a non-string token.
This commit tokenises all characters within the key as `Name::Label`.

Third, it adds support for 'bare' key-value pairs, that is text of the
form <string>: <value>. These 'bare' key-value pairs are not tokenised
the same way as they would be within objects. Rather, keys are tokenised
as ordinary strings. This preserves backwards compatability with how the
JSON lexer previously worked.

lib/rouge/lexers/json.rb

@@ -12,58 +12,66 @@ class JSON < RegexLexer
                 'application/hal+json', 'application/problem+json',
                 'application/schema+json'
 
-      state :root do
+      state :whitespace do
         rule %r/\s+/, Text::Whitespace
+      end
+
+      state :root do
+        mixin :whitespace
         rule %r/{/, Punctuation, :object
         rule %r/\[/, Punctuation, :array
+
+        rule(%r//) { push :value }
       end
 
       state :object do
-        rule %r/\s+/, Text::Whitespace
-        rule %r/"/, Str::Double, :name
+        mixin :whitespace
+        rule %r/"/, Name::Label, :name
         rule %r/:/, Punctuation, :value
         rule %r/,/, Punctuation
         rule %r/}/, Punctuation, :pop!
       end
-
+      
       state :value do
-        rule %r/"/, Name::Tag, :stringvalue
+        mixin :whitespace
+        rule %r/"/, Str::Double, :string_value
         mixin :constants
-        rule %r/}/ do
-          token Punctuation
-          pop! 2 # pop both this state and the :object one below it
-        end
         rule %r/\[/, Punctuation, :array
         rule %r/{/, Punctuation, :object
         rule %r/}/ do
-          token Punctuation
-          pop! 2 # pop both this state and the :object one below it
+          if stack[-2].name == :object
+            token Punctuation
+            pop! 2 # pop both this state and the :object one below it
+          else
+            token Error
+            pop!
+          end
         end
         rule %r/,/, Punctuation, :pop!
-        rule %r/\s+/, Text::Whitespace
+        rule %r/:/, Punctuation
       end
 
       state :name do
-        rule %r/[^\\"]+/, Str::Double
-        rule %r/\\./, Str::Escape
-        rule %r/"/, Str::Double, :pop!
+        rule %r/[^\\"]+/, Name::Label
+        rule %r/\\./, Name::Label
+        rule %r/"/, Name::Label, :pop!
       end
 
-      state :stringvalue do
-        rule %r/[^\\"]+/, Name::Tag
+      state :string_value do
+        rule %r/[^\\"]+/, Str::Double
         rule %r/\\./, Str::Escape
-        rule %r/"/, Name::Tag, :pop!
+        rule %r/"/, Str::Double, :pop!
       end
 
       state :array do
         rule %r/\]/, Punctuation, :pop!
-        rule %r/"/, Name::Tag, :stringvalue
+        rule %r/"/, Str::Double, :string_value
         rule %r/,/, Punctuation
         mixin :constants
         mixin :root
       end
 
-      state :constants do 
+      state :constants do
         rule %r/(?:true|false|null)/, Keyword::Constant
         rule %r/-?(?:0|[1-9]\d*)\.\d+(?:e[+-]?\d+)?/i, Num::Float
         rule %r/-?(?:0|[1-9]\d*)(?:e[+-]?\d+)?/i, Num::Integer