maint: Update README.

* README: Slightly change wording.

Signed-off-by: Mathieu Lirzin <mthl@gnu.org>

README

-Cuirass is continuous integration system using GNU Guix.  It is
-intended as replacement for Hydra.
+Cuirass is a continuous integration tool using GNU Guix.  It is intended as a
+replacement for Hydra.
 
 Requirements
 ============
@@ -32,9 +32,9 @@ This will read the file "tests/hello-singleton.scm" which contains a list of
 specifications and add them to the database "test.db" which is created if it
 doesn't already exist.
 
-cuirass then loops evaluating/building the specs.  The database keeps track of
-the specifications in order to allow users to accumulate specifications.  To
-resume the evaluation/build process you can execute the same command without
-the specifications option:
+'cuirass' then loops evaluating/building the specs.  The database keeps track
+of the specifications in order to allow users to accumulate specifications.
+To resume the evaluation/build process you can execute the same command
+without the '--specifications' option:
 
   ./pre-inst-env cuirass --database=test.db