proposal to fix #74: add reply button

- added "reply" button to the left of the "delete" button
- removed the click listener from the .post-content

NOTE: I'm not sure if this is actually the best solution. I thought of two other variants
2. make it completely "unobtrusive" and not only add the click listener via JS but also the button
3. add the form directly and only control visibility via JS

Comments very welcome.