Update main README file

Brings the "Running" section up to date and mentiones the new flag
"benchmark-generators"

README.md

@@ -4,17 +4,21 @@
 
     stack build
 
-Alternatively, you can directly download the [latest binaries for linux](https://gitlab.cs.fau.de/i8/copar/-/jobs/artifacts/master/download?job=test).
+Alternatively, you can directly download the [latest binaries for
+linux](https://gitlab.cs.fau.de/i8/copar/-/jobs/artifacts/master/download?job=test).
 
-## Running
+Enabling the flag `benchmark-generators` also build generators and helper
+executables used to create various benchmark suites that have been used in
+different publications. To build with that flag, use the command `stack build
+--flag copar:benchmark-generators`.
 
-There isn't much to see, yet. To see pretty printed parse results,
-use:
+## Running
 
-    stack exec copar refine < FILENAME
+To partition states of a coalgebra specification, use the command
 
-Where `FILENAME` is a file describing the input. Examples are in
-`examples/`.
+    stack exec -- copar refine FILENAME
+    
+Examples for input files are in the directory `examples/`.
 
 Command line syntax is described in `stack exec -- copar --help`.