Move the Tutorials section after the User Guide

This seems like a more natural order for reading the documentation. The
users can read the user guide first and then go through the tutorials to
have a more hands-on experience.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

docs/SUMMARY.md

@@ -1,5 +1,5 @@
 * [Home](index.md)
 * [User Guide](user-guide/)
-* [API Reference](reference/)
 * [Tutorials](tutorials/)
+* [API Reference](reference/)
 * [Contributing](CONTRIBUTING.md)