Add Serde Support For AST

[sodiumjoe]

branched from #77

[jondlm]

Any chance we could get this merged/released soon? I understand if y'all are busy. I'll begin the process of forking internally but ideally we can unwind that soon.

[LegNeato]

@tailhook Can you take a look?

[LegNeato]

Not sure if this is a good idea, but I think to not duplicate everything you could do something like:

#[cfg(feature = "serde")]mod text_traits {use serde::{Serialize,Deserialize};pubtraitSerdeTraits<'a>:Serialize + Deserialize<'a>{}impl<'a,T>SerdeTraits<'a>forTwhereT:Serialize + Deserialize<'a>{}}#[cfg(not(feature = "serde"))]mod text_traits {pubtraitSerdeTraits<'a>{}impl<'a,T>SerdeTraits<'a>forT{}}// Define the main trait with conditional compilationpubtraitText<'a>:'a{typeValue:'a
+ From<&'astr>
+ AsRef<str>
+ std::borrow::Borrow<str>
+ PartialEq
+ Eq
+ PartialOrd
+ Ord
+ fmt::Debug
+ Clone
+ text_traits::SerdeTraits<'a>;}