Fix the reply-to address when using the contact form.

#4920 

Before the change using auto-reply the address is wrong:
![selection_131](https://f.cloud.github.com/assets/4497748/1962893/43976acc-8290-11e3-803b-b82629279d15.png)

After the change the "to" is the right sender address:
![selection_132](https://f.cloud.github.com/assets/4497748/1962898/487d513c-8290-11e3-9f70-157d00cbdf10.png)