Add Builder.render and instance methods for tags

Builder.render takes a function that calls tag methods and returns a
view fragment.

spec/stdlib/template/builder-spec.coffee

@@ -6,6 +6,19 @@ describe "Builder", ->
 
   beforeEach -> builder = new Builder
 
+  describe "@render", ->
+    fit "runs the given function in a fresh builder instance and returns the resulting view fragment", ->
+      fragment =
+        Builder.render ->
+          @div =>
+            @ol class: 'cool-list', =>
+              @li()
+              @li()
+
+      expect(fragment).toMatchSelector('div')
+      expect(fragment.find('ol.cool-list')).toExist()
+      expect(fragment.find('li').length).toBe 2
+
   describe ".tag(name, args...)", ->
     it "can generate simple tags", ->
       builder.tag 'div'

src/stdlib/template/builder.coffee

@@ -6,6 +6,11 @@ Text = require 'template/text'
 
 module.exports =
 class Builder
+  @render: (fn) ->
+    builder = new this
+    fn.call(builder)
+    builder.toFragment()
+
   @elements:
     normal: 'a abbr address article aside audio b bdi bdo blockquote body button
       canvas caption cite code colgroup datalist dd del details dfn div dl dt em
@@ -18,6 +23,13 @@ class Builder
     void: 'area base br col command embed hr img input keygen link meta param
       source track wbr'.split /\s+/
 
+
+  @allElements: ->
+    @elements.normal.concat(@elements.void)
+
+  _.each @allElements(), (tagName) =>
+    @prototype[tagName] = (args...) -> @tag(tagName, args...)
+
   constructor: ->
     @reset()
 
@@ -37,7 +49,7 @@ class Builder
     @document.push(new OpenTag(name, options.attributes))
     if @elementIsVoid(name)
       if (options.text? or options.content?)
-        throw new Error("Self-closing tag #{tag} cannot have text or content")
+        throw new Error("Self-closing tag #{name} cannot have text or content")
     else
       options.content?()
       @text(options.text) if options.text