Fix typo in README--not building trplkt

./Build.app.htm is trplkt; main.src is for xxditb

README.markdown

@@ -5,7 +5,8 @@ Building
 ========
 
 Using `Build.app.htm` (for example, after double clicking it and then pointing
-it at the project source tree), build trplkt by running the following command:
+it at the project source tree), build with trplkt by running the following
+command:
 
     build ./main.src