fix format error.

Author: lziest

README.markdown

@@ -1464,8 +1464,10 @@ ngx-ssl-session-ticket-keys
 
 Dumping ssl session ticket keys of a nginx worker.
 
+```bash
 # assuming one nginx worker process has the pid 3781.
 $ ./samples/ngx-ssl-session-ticket-keys.sxx -I ./tapset -x 3781
+```
 
 [Back to TOC](#table-of-contents)
 
@@ -1474,8 +1476,10 @@ ngx-ssl-session-resumption-stats
 
 Analyzing the statistics of nginx SSL/TLS session ticket resumption.
 
+```bash
 # assuming one nginx worker process has the pid 3781.
 $ ./samples/ngx-ssl-session-resumption-stats.sxx -x 3781
+```
 
 [Back to TOC](#table-of-contents)