Removed length attribute.

[AlexNeises]

I would get an error when trying to generate header documentation. Removing the length check fixed the problem.

[softdevstory]

Thanks your codes.
I will review it. please give me time. :)

[softdevstory]

I tested by using examples.
There is an error.

$ node index.js -p examples -o output.md --template templates/default.md 
undefined:25
  throw err;
  ^

TypeError: ejs:44
    42| ### Header Examples
    43| 
 >> 44| <% data[group][sub][0].header.examples.forEach(function (example) { -%>
    45| ```json
    46| <%- example.content %>
    47| ```

Cannot read property 'length' of undefined
    at eval (eval at <anonymous> (/Users/developer/Softdevstory/Work/node-apidoc-markdown/node_modules/ejs/lib/ejs.js:237:14), <anonymous>:37:112)
    at Array.forEach (native)
    at eval (eval at <anonymous> (/Users/developer/Softdevstory/Work/node-apidoc-markdown/node_modules/ejs/lib/ejs.js:237:14), <anonymous>:30:962)
    at Array.forEach (native)
    at eval (eval at <anonymous> (/Users/developer/Softdevstory/Work/node-apidoc-markdown/node_modules/ejs/lib/ejs.js:237:14), <anonymous>:30:837)
    at eval (eval at <anonymous> (/Users/developer/Softdevstory/Work/node-apidoc-markdown/node_modules/ejs/lib/ejs.js:237:14), <anonymous>:48:19)
    at /Users/developer/Softdevstory/Work/node-apidoc-markdown/node_modules/ejs/lib/ejs.js:250:15
    at Object.<anonymous> (/Users/developer/Softdevstory/Work/node-apidoc-markdown/index.js:88:31)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)