Fix prompt in extract_boundary.m (#179)

* fix prompt when using `make_bc(m,'outer',0)`;

Author: Keith Roberts

README.md

@@ -147,6 +147,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## Fixed
 - Boundary labeling fix
+- Prompt when labeling bcs using `outer` kwarg in `make_bc`
 
 ### [3.3.0] - 2020-12-21
 ## Fixed

utilities/extract_boundary.m

@@ -124,7 +124,7 @@
         nbvv = boudat.nbvv;
         ibtype = boudat.ibtype;
         if ~exist('type2','var') 
-           type2 = input('What kind of flux boundary is it, 20(island),22(River)?');
+           type2 = input('What kind of flux boundary is it, 20 (Mainland), 21 (Island), 22 (River)?');
         end
         for ii = 1 : length(poly)
             nbou = nbou + 1;