Fix broken link, and added course (trailofbits#47)

Hovav Shacham now joined UT Austin, and the link in the book was broken You are absolutely right, his reading list is hard core, so I've updated it with a course he's teaching currently. I have also added a course taught by Nickolai Zeldovich, which is a great starting point for anyone trying to get a feel of security. You can add it, if you feel it's noteworthy.

intro/careers.md

@@ -72,7 +72,8 @@ If you're looking for something more hands-on and directed, there are lots of un
 | [Malware Analysis and Antivirus Technologies](http://www.tml.tkk.fi/Opinnot/T-110.6220/2008/)   | various            | TML         |
 | [System Security and Binary Code Analysis](https://www.utdallas.edu/~zxl111930/spring2012.html) | Zhiqiang Lin	      | UT Dallas   |
 | [Cybersecurity Specialization](https://www.coursera.org/specializations/cybersecurity)          | various            | UMD         |
-| [Graduate Computer Security](http://cseweb.ucsd.edu/classes/wi09/cse227/syllabus.html)          | Hovav Shacham      | UCSD        |
+| [Graduate Computer Security](https://www.cs.utexas.edu/~hovav/cs380s-f18.html)          | Hovav Shacham      | UT Austin        |
+| [Computer Systems Security](https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-858-computer-systems-security-fall-2014/)          | Nickolai Zeldovich      | MIT        |
 
 ## University
 The easiest shortcut to finding a university with a dedicated security program is to look through the [NSA Centers of Academic Excellence](http://www.nsa.gov/ia/academic_outreach/nat_cae/institutions.shtml) (NSA-COE) institution list. This certification has become watered down as more universities have obtained it and it might help to focus your search on those that have obtained the newer [COE-CO](http://www.nsa.gov/academia/nat_cae_cyber_ops/nat_cae_co_requirements.shtml) certification. Remember, certifications are only a guideline. You should look into the actual programs at each university instead of basing your decision on a certification alone.