Config validation

[nbardy]

Added some tests and testing, but it could definitely use a little more.

The code has some inconsistencies between using nil values and missing keys in options maps. The schema could be made clearer if this was standardized.

#88

[lacarmen]

This looks like a great start! Two things I'd like to change:

1. Let's move all the schema definitions into a separate namespace. I'd like to keep the noise out of the compiler namespace as it's already so length as it is.
2. {Any Any} will have to be added to the main Config schema and the MetaData schema since users can any parameter to these maps to have it available in their templates. (The relevant PR is here)

[lacarmen]

Comments not related to the code review:

Another thing that I would change is to have separate MetaData schemas for pages and posts since not all keys are shared between them (home? and navbar?, for example). However, this requires reworking how post/page content is read so I'm okay with leaving this one for later.

I agree there are some weird inconsistencies with how nils/missing keys are dealt with. These ones I can consolidate on my own.

[jerger]

Great work :-)
Have you ever looked at (schema/defn ^:always-validate ...) ?

This would allow to validate parameters & result of a function - you will need no additional (schema/validate ...).

Usage is:

(schema/defn ^:always-validate 
    fn-name :- result-schema
    "doc-string"
    [param1 :- param1-schema
     ...]
) 

[lacarmen]

Hey @nbardy are you still working on this?

[lacarmen]

Going to merge this to keep things moving along. I'll make the requested changes myself.