travis: simplify commands

We do everything with tox, so the MODE environment variable is really just a
tox environment identifier

.travis.yml

@@ -6,6 +6,7 @@ before_cache:
   - rm -f $HOME/.cache/pip/log/debug.log
 git:
   depth: 1000
+
 install:
 # ~/.local/bin is on $PATH by default, but on OS-X, --user puts it elsewhere
   - if [ "${TRAVIS_OS_NAME}" = "osx" ]; then export PATH=$HOME/Library/Python/2.7/bin:$PATH; fi
@@ -15,13 +16,14 @@ install:
   - if [ "${TRAVIS_OS_NAME}" = "linux" ]; then pip install --upgrade codecov tox setuptools; fi
   - echo $PATH; which python; which pip; which tox
   - python misc/build_helpers/show-tool-versions.py
+
 script:
-  - if [ "${MODE}" = "codechecks" ]; then tox -e codechecks; fi
-  - if [ "${MODE}" = "tests" ]; then tox; fi
-  - if [ "${MODE}" = "coverage" ]; then tox -e coverage; fi
-  - if [ "${MODE}" = "integration" ]; then /bin/bash integration/install-tor.sh && tox -e integration; fi
+  - if [ "${T}" = "integration" ]; then /bin/bash integration/install-tor.sh; fi
+  - tox -e ${T}
+
 after_success:
-  - if [ "${MODE}" = "coverage" ]; then codecov; fi
+  - if [ "${T}" = "coverage" ]; then codecov; fi
+
 notifications:
   email: false
   irc:
@@ -31,17 +33,18 @@ notifications:
     template:
       - "%{repository}#%{build_number} [%{branch}: %{commit} by %{author}] %{message}"
       - "Changes: %{compare_url} | Details: %{build_url}"
+
 matrix:
   include:
   - os: linux
-    env: MODE=coverage LANG=en_US.UTF-8
+    env: T=coverage LANG=en_US.UTF-8
   - os: linux
-    env: MODE=integration LANG=en_US.UTF-8
+    env: T=integration LANG=en_US.UTF-8
   - os: linux
-    env: MODE=codechecks LANG=en_US.UTF-8
+    env: T=codechecks LANG=en_US.UTF-8
   - os: linux
-    env: MODE=tests LANG=C
+    env: T=py27 LANG=C
   - os: osx
-    env: MODE=tests LANG=en_US.UTF-8
+    env: T=py27 LANG=en_US.UTF-8
     language: generic  # "python" is not available on OS-X
   fast_finish: true