write hook creates a directory if it doesnt exist

- thanks to @monkeez for this
- closes #438

lib/compiler.coffee

@@ -6,6 +6,7 @@ nodefn   = require 'when/node'
 pipeline = require 'when/pipeline'
 sequence = require 'when/sequence'
 File     = require 'vinyl'
+mkdirp   = require 'mkdirp'
 
 ###*
  * @class Compiler
@@ -204,7 +205,8 @@ class CompileFile
 
     obj.path = @roots.config.out(obj.path, obj.extension)
 
-    nodefn.call(fs.writeFile, obj.path, obj.content)
+    nodefn.call(mkdirp, path.dirname(obj.path))
+      .then(-> nodefn.call(fs.writeFile, obj.path, obj.content))
 
   ###*
    * Read the file's extension and grab any and all adapters that match. If

test/extensions_test.coffee

@@ -75,6 +75,8 @@ describe 'write hook', ->
     path.join(@public, 'multi1.html').should.have.content('clone 1')
     path.join(@public, 'multi2.html').should.be.a.file()
     path.join(@public, 'multi2.html').should.have.content('clone 2')
+    path.join(@public, 'subdir/multi3.html').should.be.a.file()
+    path.join(@public, 'subdir/multi3.html').should.have.content('clone 3')
 
 describe 'categories', ->
 

test/fixtures/extensions/write_hook/app.coffee

@@ -42,6 +42,7 @@ write_multiple = ->
         [
           { path: path.join(ctx.roots.root, 'multi1.html'), content: 'clone 1' },
           { path: path.join(ctx.roots.root, 'multi2.html'), content: 'clone 2' }
+          { path: path.join(ctx.roots.root, 'subdir/multi3.html'), content: 'clone 3' }
         ]
 
 module.exports =