adding in support for common LinkedIn fork features

this adds in support for common linkedin fork features-

* kwargs in partials ( first commit )

* some inline docs added  (second commit)

* added compatibility matrix (third commit)

* consolidated Context's `get_path` and `get` ; now handles outside scope

kwargs in partials; addressing https://github.com/mahmoud/ashes/issues/14

a few notes: kwargs

1- I removed the `bodies` arg into the partials render and replaced it with `params` kwargs.  i couldn't find a basis/rationale for the `bodies` ever being supplied into this function.

2- i included two ways of pulling this off:

*  use a dedicated partial context ( and new `make_base` function )
*  replicate how `section` works with a `context.push(`

the latter is enabled.

3- this patch required the tests to be changed , as they now should expect a 'params' entry with partials.


a few notes: path resolution

1. this could probably use some more tests to ensure that paths starting with a '.' are handled correctly

2. i think i handled implementing helpers correctly, but that could use a second look.