Travis: run on ubuntu trusty container-based images (#101)

Use trusty (Ubuntu 14.04) for travis. Don't version lock requirements. This should not affect non-travis users because the bug in requests has been fixed to my knowledge.

.travis.yml

@@ -1,8 +1,10 @@
 sudo: false # force container-based builds (no start-up time!)
 
+dist: trusty # force 14.04 trusty build
+
 language: python
 
-cache: pip # enable cache for "$HOME/.pip-cache" directory
+cache: pip # enable cache for "$HOME/.cache/pip" directory
 
 before_install:
   - export CFLAGS=-O0 # considerably speed-up build time for pip packages (especially lxml), optimizations doesn't matter for ci
@@ -10,7 +12,7 @@ before_install:
   - python verify_files.py # make sure input files are OK before wasting time with prereqs
 
 install:
-  - pip install -r requirements.txt --cache-dir $HOME/.pip-cache
+  - pip install -r requirements.txt
 
 script: bash ./deploy.sh
 

requirements.txt

@@ -1,7 +1,7 @@
-requests==2.13.0
+requests
 feedparser
 lxml
 Pillow
 datetime
 beautifulsoup4
-commentjson
+commentjson