Add decorator support to Python (#1639)

Add support for Python decorators, implementing #1635
using the solution proposed by @spectras.

Also add 2 aliases: `annotation` to be like Java and `punctuation`
to change the actual color (like Java).

This resolves #1635.

components/prism-python.js

@@ -20,8 +20,16 @@ Prism.languages.python = {
 		pattern: /(\bclass\s+)\w+/i,
 		lookbehind: true
 	},
+	'decorator': {
+		pattern: /(^\s*)@\w+(?:\.\w+)*/i,
+		lookbehind: true,
+		alias: ['annotation', 'punctuation'],
+		inside: {
+			'punctuation': /\./
+		}
+	},
 	'keyword': /\b(?:and|as|assert|async|await|break|class|continue|def|del|elif|else|except|exec|finally|for|from|global|if|import|in|is|lambda|nonlocal|not|or|pass|print|raise|return|try|while|with|yield)\b/,
-	'builtin':/\b(?:__import__|abs|all|any|apply|ascii|basestring|bin|bool|buffer|bytearray|bytes|callable|chr|classmethod|cmp|coerce|compile|complex|delattr|dict|dir|divmod|enumerate|eval|execfile|file|filter|float|format|frozenset|getattr|globals|hasattr|hash|help|hex|id|input|int|intern|isinstance|issubclass|iter|len|list|locals|long|map|max|memoryview|min|next|object|oct|open|ord|pow|property|range|raw_input|reduce|reload|repr|reversed|round|set|setattr|slice|sorted|staticmethod|str|sum|super|tuple|type|unichr|unicode|vars|xrange|zip)\b/,
+	'builtin': /\b(?:__import__|abs|all|any|apply|ascii|basestring|bin|bool|buffer|bytearray|bytes|callable|chr|classmethod|cmp|coerce|compile|complex|delattr|dict|dir|divmod|enumerate|eval|execfile|file|filter|float|format|frozenset|getattr|globals|hasattr|hash|help|hex|id|input|int|intern|isinstance|issubclass|iter|len|list|locals|long|map|max|memoryview|min|next|object|oct|open|ord|pow|property|range|raw_input|reduce|reload|repr|reversed|round|set|setattr|slice|sorted|staticmethod|str|sum|super|tuple|type|unichr|unicode|vars|xrange|zip)\b/,
 	'boolean': /\b(?:True|False|None)\b/,
 	'number': /(?:\b(?=\d)|\B(?=\.))(?:0[bo])?(?:(?:\d|0x[\da-f])[\da-f]*\.?\d*|\.\d+)(?:e[+-]?\d+)?j?\b/i,
 	'operator': /[-+%=]=?|!=|\*\*?=?|\/\/?=?|<[<=>]?|>[=>]?|[&|^~]/,

tests/languages/python/decorator_feature.test

@@ -0,0 +1,28 @@
+@some.decorator(foobar)
+def foo(bar):
+    pass
+
+----------------------------------------------------
+
+[
+	["decorator", [
+		"@some",
+		["punctuation", "."],
+		"decorator"]
+	],
+	["punctuation", "("],
+	"foobar",
+	["punctuation", ")"],
+
+	["keyword", "def"],
+	["function", "foo"],
+	["punctuation", "("],
+	"bar",
+	["punctuation", ")"],
+	["punctuation", ":"],
+	["keyword", "pass"]
+]
+
+----------------------------------------------------
+
+Checks for decorators.