Document and test "page" and "rows_per_page" parameters.

Closes #123

doc/API.md

@@ -34,6 +34,15 @@ Supported query string parameters:
               timestamp value in cache_buster for manual control of
               updates.
 
+  'rows_per_page':
+              Limit the number of rows in output. Affects all formats,
+              see also 'page'.
+
+  'page':
+              When 'rows_per_page' is used to limit rows, 'page' can be
+              used to specify which page to start returning rows from.
+              First page has index 0.
+
 Response formats
 ----------------
 

test/acceptance/app.test.js

@@ -216,6 +216,28 @@ function(done){
     });
 });
 
+// Test page and rows_per_page params
+test("paging", function(done){
+    assert.response(app, {
+        url: '/api/v1/sql?' + querystring.stringify({
+          // note: select casing intentionally mixed
+          q: 'SELECT * FROM (VALUES(1),(2),(3),(4),(5),(6),(7),(8),(9)) t(v)',
+          rows_per_page: 3,
+          page: 2
+        }),
+        headers: {host: 'vizzuality.cartodb.com'},
+        method: 'GET'
+    },{ }, function(res) {
+        assert.equal(res.statusCode, 200, res.body);
+        var parsed = JSON.parse(res.body);
+        assert.equal(parsed.rows.length, 3);
+        assert.equal(parsed.rows[0].v, 7);
+        assert.equal(parsed.rows[1].v, 8);
+        assert.equal(parsed.rows[2].v, 9);
+        done();
+    });
+});
+
 test('POST /api/v1/sql with SQL parameter on SELECT only. no database param, just id using headers', function(done){
     assert.response(app, {
         url: '/api/v1/sql',