README draft.

README.md

@@ -1,2 +1,20 @@
 # qcron
-Qt cron-like scheduler
+
+qcron is a cron-like scheduler based on Qt. Using a pattern following
+cron syntax, a QCron object will emit signals when the system time
+(given by QDateTime) enters a valid time table or when it leaves such
+time table.
+
+# Exemple
+
+```c++
+/* From monday to friday, every minutes from 8:00 to 11:59 and from
+14:00 to 17:59. */
+QCron cron("* 8-11,14-17 * * 1-5 *");
+connect(&cron, SIGNAL(activated()),   this, SLOT(onActivation()));
+connect(&cron, SIGNAL(deactivated()), this, SLOT(onDeactivation()));
+```
+
+The 'activated' signal will be emitted every weekday at 8.00 and
+14.00, and the 'deactivated' signal will be emitted every weekday at
+12.00 and 18.00.