Add tests for explicit context setting that check failure conditions and implement a helper function to generate a new breadcrumb stack.

src/parser/mod.rs

@@ -9,6 +9,7 @@ pub use parser::Filter;
 pub use parser::KVPair;
 pub use parser::OwnedLiteral;
 pub use parser::PartialNameElement;
+pub use parser::Path;
 pub use parser::RValue;
 pub use parser::Special;
 pub use parser::Template;