Cache pip and all that

Author: natanlao

.travis.yml

@@ -1,6 +1,8 @@
 language: python
 dist: xenial  # for python3.7+ testing
 
+cache: pip
+
 python:
 - 3.6
 - 3.7
@@ -15,6 +17,6 @@ install:
 
 script:
 # Test that notebooks run successfully
-- N=`awk '{printf " --exclude " $0}' test/ignore` treon ${!N}
+- exclude="$(awk '{printf " --exclude " $0}' test/ignore)" eval "treon $exclude"
 # Naive test to check that output committed with notebook-
 - find . -name "*.ipynb" -exec sh test/test_output.sh "{}" \;