post_url tag issues

[WalkerCodeRanger]

Using pretzel 0.2.1.169 (build 175) which I downloaded from Appveyor (non script cs zip), the post_url tag doesn't respect the permalink setting and also I am pretty sure it is supposed to generate with a leading slash.

Steps to reproduce

1. pretzel create
2. edit _config.yaml to add permalink: /blog/:year/:month/:title/ at the end (note trailing slash to avoid issue Extensionless permalinks #244)
3. edit _posts\2015-05-05-myfirstpost.md to add {% post_url 2015-05-05-myfirstpost %} before hello world
4. pretzel taste
5. Click the "My First Post" title to go to http://localhost:8080/blog/2015/05/myfirstpost/

You'll see "2015/05/05/myfirstpost.html" at the top of the post. This is generating a url using the standard permalink scheme instead of the configured one. Also I am pretty sure that there should be a leading slash. That is based on how I was always able to use post_url in my jekyll site for github. Also, the docs show an example of [Name of Link]({% post_url 2010-07-21-name-of-post %}) which would only make sense if the url had a leading slash. So, the link should be "/blog/2015/05/myfirstpost/"

[laedit]

Right now the PostUrlTag is totally isolated and don't have the necessary information about the pages to do his job correctly.
The problem is that currently DotLiquid create a new instance of the tag just before using it, so I am waiting for dotliquid/dotliquid#150 to fix this.