Update documentation

CONTRIBUTING.md

@@ -6,7 +6,7 @@ Tips for contributors
   branch and is subsequently merged into `master` for releases.
 * If you're making **changes to files for which the Travis build is not
   relevant**, please **add `[ci skip]` to the end of the commit message**.
-* Report bugs using [Bugzilla].  If you want, you can access the bug system using the lite (free) version of [Deskzilla]. 
+* Report bugs using [GitHub Issues].
 
 GLOSSARY
 ----
@@ -119,8 +119,7 @@ cores:
 
 [Boost]: http://boost.org
 [Boost.Python]: http://www.boost.org/libs/python/
-[Bugzilla]: http://bugs.ledger-cli.org/
-[Deskzilla]: http://almworks.com/deskzilla/download.html
+[GitHub Issues]: https://github.com/ledger/ledger/issues
 [GMP]: http://gmplib.org/
 [MPFR]: http://www.mpfr.org/
 [Cheetah]: http://www.cheetahtemplate.org

INSTALL.md

@@ -96,10 +96,10 @@ A: Actually, the real segfault is in libstdc++'s facet code.  It's being
 
 Q: Something else fails, or Ledger crashes on startup
 
-A: This, I am most interested in hearing about.  Please file a bug
-  at the Ledger Bugzilla, http://bugs.ledger-cli.org/.  The more
-  details you can provide, the better.  Also, if Ledger is crashing,
-  try running it under gdb like so:
+A: This, I am most interested in hearing about.  Please file a bug at the
+  Ledger Issue Tracker, https://github.com/ledger/ledger/issues.  The more
+  details you can provide, the better.  Also, if Ledger is crashing, try
+  running it under gdb like so:
 
     $ gdb ledger
     (gdb) run <ARGS TO LEDGER>