Switch back to travis containers

As gmime was white-listed upstream we can install it with the APT addon and
don't need sudo any longer.

.travis.yml

@@ -4,8 +4,6 @@ language: python
 # in precise.
 dist: trusty
 
-sudo: true
-
 python:
   # We can add more version strings here when we support other python
   # versions.
@@ -25,23 +23,18 @@ addons:
       - libxapian-dev
       - libtalloc-dev
       - zlib1g-dev
+      - libgmime-2.6-dev
 
 # Build notmuch and the python notmuch libs manually.  The versions of the
 # notmuch library and the python module which are available in the 12.04 and
 # 14.04 Ubuntu repos do not match and do not fullfill the version requirement
 # for alot.
 before_install:
-  - sudo apt-get update
-  # Until https://github.com/travis-ci/apt-package-whitelist/issues/3215 is
-  # resolved we have to install gmime with sudo.  Afterwards we can swtich to
-  # the container based infrastructure.
-  # gmime is needed to build notmuch from source.
-  - sudo apt-get -yqq install libgmime-2.6-dev
   # Clone the notmuch repository and move into it.
   - git clone git://notmuchmail.org/git/notmuch
   - cd notmuch
-  # Make and install the library.  We install the library without sudo as we
-  # might want to switch to the travis container later.
+  # Make and install the library.  We install the library without sudo beacuse
+  # we want to use the travis container and that doesn't allow sudo.
   - ./configure --prefix=$HOME/.local
   - make
   - make install
@@ -64,7 +57,7 @@ install:
   - pip --quiet install sphinx
 
 before_script:
-  # Prepare a minimal config file for the final test.
+  # Prepare a minimal config file for the minimal test.
   - touch ~/.notmuch-config
   - echo 'initial_command=call os._exit(0)' > conf