update README with usage output

README

@@ -1,7 +1,26 @@
-script for Evolix maintenance
-=============================
+# Evomaintenance
 
-script evomaintenance.sh which sends a mail
-for each intervention on a Pack Evolix server.
+```
+# evomaintenance --help
+evomaintenance is a program that helps reporting what you've done on a server
 
-* Pb quand '&' dans le msg d'evomaintenance...
+Usage: evomaintenance
+  or   evomaintenance --message="add new host"
+  or   evomaintenance --no-db --no-mail --no-commit
+  or   echo "add new vhost" | evomaintenance
+
+Options
+ -m, --message=MESSAGE       set the message from the command line
+     --mail                  enable the mail hook (default)
+     --no-mail               disable the mail hook
+     --db                    enable the database hook (default)
+     --no-db                 disable the database hook
+     --commit                enable the commit hook (default)
+     --no-commit             disable the commit hook
+     --auto                  use "auto" mode
+     --no-auto               use "manual" mode (default)
+ -v, --verbose               increase verbosity
+ -n, --dry-run               actions are not executed
+     --help                  print this message and exit
+     --version               print version and exit
+```