Add libsodium dependency as a PPA to Travis file

Author: lgrahl

.travis-install-libsodium.sh

@@ -1,15 +1,22 @@
 # Use container system
 sudo: false
 
-# Cache pip & libsodium
+# Install APT dependencies
+addons:
+  apt:
+    sources:
+    - sourceline: "ppa:chris-lea/libsodium"
+    packages:
+    - libsodium-dev
+
+# Cache pip
 cache:
   directories:
-  - $HOME/libsodium
   - $HOME/.cache/pip
 
 # Clean up pip log
 before_cache:
-  - rm -f $HOME/.cache/pip/log/debug.log
+- rm -f $HOME/.cache/pip/log/debug.log
 
 # Build matrix
 language: python
@@ -55,37 +62,34 @@ matrix:
 # TODO: Re-enable once pypy3 is able to compile uvloop
 #  - python: "pypy3"  # 2017-08-05: It's pypy3-5.8.0-beta
 #    env:
-#      - EVENT_LOOP=uvloop
-#      - TIMEOUT=16.0
+#    - EVENT_LOOP=uvloop
+#    - TIMEOUT=16.0
 #    before_script: "pip install .[uvloop]"
 
 # Install dependencies
-before_install:
-  - ./.travis-install-libsodium.sh
-  - export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:${HOME}/libsodium/lib
 install:
-  - pip install -U setuptools pip
-  - "pip install .[dev]"
-  - pip install codecov
+- pip install -U setuptools pip
+- "pip install .[dev]"
+- pip install codecov
 
 # Run flake8, isort, check docs & tests
 # TODO: Re-enable isort once #85 has been resolved
 script:
-  - >
-    if [[ "$TRAVIS_PYTHON_VERSION" != "pypy3" ]]; then
-      flake8 . || travis_terminate 1;
-      #isort -rc -c . || (isort -rc -df . && return 1) || travis_terminate 1;
-    fi
-  - python setup.py checkdocs
-  - >
-    py.test \
-      --ignore=$IGNORE \
-      --cov-config .coveragerc \
-      --cov=saltyrtc.server \
-      --loop=$EVENT_LOOP \
-      --timeout=$TIMEOUT
+- >
+  if [[ "$TRAVIS_PYTHON_VERSION" != "pypy3" ]]; then
+    flake8 . || travis_terminate 1;
+    #isort -rc -c . || (isort -rc -df . && return 1) || travis_terminate 1;
+  fi
+- python setup.py checkdocs
+- >
+  py.test \
+    --ignore=$IGNORE \
+    --cov-config .coveragerc \
+    --cov=saltyrtc.server \
+    --loop=$EVENT_LOOP \
+    --timeout=$TIMEOUT
 
 # After success
 after_success:
-  - codecov
+- codecov