docs: Use modules link in the documentation index page

Module docs contain more information (and more content is supposed to be
added in the future) than the documentation of the structs themselves.

src/lib.rs

@@ -22,12 +22,13 @@
 //!
 //! ## Algorithms
 //!
-//! * [Trust region](solver::TrustRegion) -- Recommended method to be used as a
+//! * [Trust region](solver::trust_region) -- Recommended method to be used as a
 //!   default and it will just work in most of the cases.
-//! * [Cuckoo search](solver::Cuckoo) -- A global optimization algorithm useful
+//! * [Cuckoo search](solver::cuckoo) -- A global optimization algorithm useful
 //!   for initial guesses search in combination with a numerical solver.
-//! * [Nelder-Mead](solver::NelderMead) -- Not generally recommended, but may be
-//!   useful for low-dimensionality problems with ill-defined Jacobian matrix.
+//! * [Nelder-Mead](solver::nelder_mead) -- Not generally recommended, but may
+//!   be useful for low-dimensionality problems with ill-defined Jacobian
+//!   matrix.
 //!
 //! ## Problem
 //!