New tincd post-auth BOF exploit module

A pull request to get some feedback. I'd appreciate if you comment as well on the following:
- additional class in module (if it should be relocated, an example would be helpful, e.g. which mixins etc.)
- puts calls in the additional class
- exploit development and other comments welcome?
- Fedora ROP is on my TODO list (but I wanted to contribute the module before Christmas/holidays)
- Although I left "average ranking" in there, the exploit works for all targets with several tested (meterpreter, reverse_tcp, exec) payloads on the first execution run and is therefore very reliable.
you can shorten these 2 lines into a ternary like:

```Ruby
cd = datastore['BINARY_DROP_LOCATION'] == '.' ? '' : "cd #{datastore['BINARY_DROP_LOCATION']};"
```
which might be too long, in which case you can do the following (or if you want to save 1 hash lookup):

```Ruby
bin_drop_loc = datastore['BINARY_DROP_LOCATION']
cd = bin_drop_loc == '.' ? '' : "cd #{bin_drop_loc};"
```