I've been writing tests for crypto libraries in Python, and have wanted to write
code along the lines of
```py
md5.hash(b"some message") # $ HashInput=b"some message"
```
which didn't work before this commit, forcing me to store my text in a variable
like below. This turned out to be really annoying when dealing with more complex
examples, so therefore I'm adding this new functionality to allow this behavior.
```py
msg = b"some message"
md5.hash(msg) # $ HashInput=msg
```
In preparation for adding this to Python, I have split out the
definition of the comment class in a separate file (which will be
specific to each language).
