add test and readme

test/data/nested-whitespace/data.json

@@ -0,0 +1,4 @@
+{
+    "xarray": [0, 1],
+    "yarray": [0, 1, 2]
+}

test/data/nested-whitespace/result.txt

@@ -0,0 +1,6 @@
+0-0
+0-1
+0-2
+1-0
+1-1
+1-2

test/data/nested-whitespace/template.txt

@@ -0,0 +1,3 @@
+{% for x in xarray %}{% for y in yarray %}
+{{x}}-{{y}}
+{% endfor %}{% endfor %}