readme update

README.md

@@ -19,12 +19,13 @@ A work in progress.
 
   * Is object-oriented.
   * Works with square, under-determined, or over-determined systems.
-  * Three different methods to solve the linear system:
+  * Can use different methods to solve the linear system:
     1. [LAPACK](https://www.netlib.org/lapack/) routines (`dgesv` or `dgels`) for dense systems: If `n=m`, uses `dgesv` (LU decomposition). If `n/=m`, uses `dgels` (if `m>n` uses QR factorization, if `m<n` uses LQ factorization).
     2. [lsqr](https://github.com/jacobwilliams/LSQR) -- a conjugate-gradient type method for solving sparse linear equations and sparse least-squares problems.
     3. [lusol](https://github.com/jacobwilliams/lusol) -- A sparse LU factorization for square and rectangular matrices, with Bartels-Golub-Reid updates for column replacement and other rank-1 modifications.
     4. [lsmr](https://github.com/jacobwilliams/LSMR) -- a conjugate-gradient type method for solving sparse linear equations and sparse least-squares problems
-  * Has a Broyden update option.
+    5. The user can also provide a custom linear solver.
+  * Has a Broyden update option (sparse and dense versions).
   * Has various line search options.
      * use a specified constant step size (0,1]
      * backtracking linesearch method