moban version 6 api update

[chfw]

_reference: moremoban/moban#302

No longer, the first parameter is a list of directories but an instance of fs.multifs.MultFS.

as the following:

class Engine(object):
    def __init__(self, template_fs, options=None):
```_

[chfw]

without this update, moban-mako will not be compatible with moban 0.6.x +.

And a program endeavour is required to write a new template lookup using pyfilesystem 2 interface

https://github.com/sqlalchemy/mako/blob/master/mako/lookup.py

class PyfilesystemLookup(TemplateLookup):
     ...

[chfw]

@PrajwalM2212 any interests in updating it?