Merge pull request #103 from mikebrow/path-to-runc

small amount of error checking and help for path to the runtime

README.md

@@ -62,6 +62,10 @@ $ sudo make install
 ```
 # ocid --debug
 ```
+If the default --runtime value does not point to your runtime:   
+```
+# ocid --runtime $(which runc)
+```
 
 #### Create a pod
 ```

cmd/server/main.go

@@ -88,6 +88,10 @@ func main() {
 			}
 			logrus.SetOutput(f)
 		}
+		if _, err := os.Stat(c.GlobalString("runtime")); os.IsNotExist(err) {
+			// path to runtime does not exist
+			return fmt.Errorf("invalid --runtime value %q", err)
+		}
 		switch c.GlobalString("log-format") {
 		case "text":
 			// retain logrus's default.