move IPA-specific methods to the provider (#138)

src/lib.rs

@@ -1,7 +1,15 @@
 //! This library implements Nova, a high-speed recursive SNARK.
+#![deny(
+  warnings,
+  unused,
+  future_incompatible,
+  nonstandard_style,
+  rust_2018_idioms,
+  missing_docs
+)]
 #![allow(non_snake_case)]
 #![allow(clippy::type_complexity)]
-#![deny(missing_docs)]
+#![forbid(unsafe_code)]
 
 // private modules
 mod bellperson;