Update travis build

.travis.yml

@@ -3,6 +3,8 @@ python:
   - 2.7
 # command to install dependencies, e.g. pip install -r requirements.txt --use-mirrors
 install:
+  - pip install arxiv2bib
+  - pip install tear-pages
   - pip install requesocks
   - pip install pyPDF2
   - pip install isbntools