feat: Create parent directories if --split-exp is used.

Problem: When --split-exp is used and produces filenames with slashes in
them, the target directories must already exist otherwise yq fails.

Fix/feature: Create the necessary directories with os.MkdirAll().
The permissions 0750 were chosen to satisfy the vulnerability checker.

acceptance_tests/split-printer.sh

@@ -2,6 +2,7 @@
 
 setUp() {
   rm test*.yml || true
+  rm -rf test_dir* || true
 }
 
 testBasicSplitWithName() {
@@ -204,4 +205,23 @@ EOM
   assertEquals "$expectedDoc3" "$doc3"
 }
 
-source ./scripts/shunit2
+testSplitWithDirectories() {
+  cat >test.yml <<EOL
+f: test_dir1/file1
+---
+f: test_dir2/dir22/file2
+---
+f: file3
+EOL
+
+  ./yq e --no-doc -s ".f" test.yml
+
+  doc1=$(cat test_dir1/file1.yml)
+  assertEquals "f: test_dir1/file1" "$doc1"
+  doc2=$(cat test_dir2/dir22/file2.yml)
+  assertEquals "f: test_dir2/dir22/file2" "$doc2"
+  doc3=$(cat file3.yml)
+  assertEquals "f: file3" "$doc3"
+}
+
+source ./scripts/shunit2