Allow to use rouge-style as alias for rouge-theme

Fixes #3

.rubocop.yml

@@ -23,13 +23,16 @@ Metrics/AbcSize:
   Max: 36
 
 Metrics/CyclomaticComplexity:
-  Max: 8
+  Max: 10
 
 Metrics/LineLength:
   Max: 100
 
 Metrics/MethodLength:
-  Max: 30
+  Max: 32
+
+Metrics/PerceivedComplexity:
+  Max: 10
 
 Style/Next:
   Enabled: false

README.adoc

@@ -59,6 +59,9 @@ rouge-theme::
   Look into https://github.com/jneen/rouge/tree/master/lib/rouge/themes[lib/rouge/themes] in the Rouge repository for a list of available themes.
   Default is `github`.
 
+rouge-style::
+  Alternative name for the `rouge-theme` for compatibility with _asciidoctor-pdf_ (see https://github.com/{gh-name}/issues/3[#3]).
+
 
 == License
 

lib/asciidoctor/rouge/treeprocessor.rb

@@ -91,7 +91,11 @@ def process_listing(block)
       block.set_attr('language', lexer.tag)
 
       if document.attr?('rouge-css', 'style')
-        opts[:inline_theme] = document.attr('rouge-theme', DEFAULT_THEME)
+        # 'rouge-style' is alternative name for compatibility with
+        # asciidoctor-pdf (see #3).
+        opts[:inline_theme] = document.attr('rouge-theme') \
+                           || document.attr('rouge-style') \
+                           || DEFAULT_THEME
       end
 
       if block.attr?('highlight', nil, false)