Added support for Travis cache (issue exercism#23)

.travis.yml

@@ -15,3 +15,4 @@ script:
 cache:
   directories:
   - $HOME/.cache/bower/
+  - $HOME/.exercise_cache/

bin/test.sh

@@ -2,21 +2,43 @@
 
 # TEST
 
+xpurescript=$(dirname "$BASH_SOURCE")
+xpurescript=$(readlink -f "$xpurescript/..")
+cd "$xpurescript"
+echo "xpurescript: $xpurescript"
+
+cache_dir="$HOME"
+if [ -z "$TRAVIS" ]; then
+  cache_dir="$xpurescript"
+fi
+cache_dir="$cache_dir/.exercise_cache"
+echo "cache_dir: $cache_dir"
+
 declare -i TEST_RESULT=0
 FAILED_EXERCISES=''
 
-for exercise_dir in exercises/**
-do
-  exercise_src="$exercise_dir/src"
-  exercise_examples_src="$exercise_dir/examples/src"
-
-  mv "$exercise_src" "$exercise_src.impl"
-  mv "$exercise_examples_src" "$exercise_src"
+cd exercises
 
+for exercise_dir in *
+do
   echo "-------------------------------------------------------"
   echo "Testing $exercise_dir"
 
   cd "$exercise_dir"
+
+  exercise_src=src
+  exercise_examples_src=examples/src
+  exercise_output=output
+  exercise_cache="$cache_dir/$exercise_dir/$exercise_output"
+
+  # Make Travis cache folder for this exercise
+  mkdir -p "$exercise_cache"
+  ln -f -s "$exercise_cache"
+  echo "exercise_cache: $(ls -l "$exercise_output")"
+
+  mv "$exercise_src" "$exercise_src.impl"
+  mv "$exercise_examples_src" "$exercise_src"
+
   bower install
   pulp test
 
@@ -27,9 +49,10 @@ do
   fi
 
   # be kind, rewind
-  cd -
   mv "$exercise_src" "$exercise_examples_src"
   mv "$exercise_src.impl" "$exercise_src"
+
+  cd -
 done
 
 if [ $TEST_RESULT -ne 0 ]; then