Update p0f to version 3.0.7b, add test

- Update p0f to version 3.0.7b.
- Add a simple test in which p0f reads a pcap file.

In the test we write a simple binary pcap file (included in the recipe base64-encoded) and then attempt to read the file with p0f.
Use full path to p0f executable in test
Correct path to p0f and test.pcap
Use relative path to test file

Reverted last commits use of the full path to the test file.
The executable is tested from within the `testpath`, so it's unnecessary.
Use double-quotes on lines w/ string interpolation
p0f: add 3.07b bottle.