Use Travis' container-based infrastructure.

Since it now supports whitelisted APT repositories and packages, which
include those LOOT needs.

.travis.yml

@@ -1,15 +1,24 @@
+sudo: false
 language: cpp
 compiler:
   - gcc
 
 cache: apt
 
-before_install:
-  # Need Boost 1.54+, which isn't in the 12.04 repositories - install from a PPA.
-  # Also need the OpenSSL dev package, for git clone from HTTPS URLs support.
-  - sudo add-apt-repository ppa:boost-latest/ppa -y
-  - sudo apt-get update -qq
-  - sudo apt-get install libboost-log1.55-dev libboost-date-time1.55-dev libboost-thread1.55-dev libboost-filesystem1.55-dev libboost-locale1.55-dev libboost-iostreams1.55-dev libssl-dev
+# Need Boost 1.54+, which isn't in the 12.04 repositories - install from a PPA.
+# Also need the OpenSSL dev package, for git clone from HTTPS URLs support.
+addons:
+  apt:
+    sources:
+      - boost-latest
+    packages:
+      - libboost-log1.55-dev
+      - libboost-date-time1.55-dev
+      - libboost-thread1.55-dev
+      - libboost-filesystem1.55-dev
+      - libboost-locale1.55-dev
+      - libboost-iostreams1.55-dev
+      - libssl-dev
 
 install:
   # Currently inside the cloned repo path.