Tests have been failing because -- I guess -- python 3.4 can't unpack
two lists in the same list of arguments.

- Create constants for the separators
- Create methods to generate the header text
- Create method to parse the header text
- Fix tests

timestamps

and include them in the header str.

This reverts commit 628d21a9.

This reverts commit 0b048e91.

This reverts commit c8b47bb5.

I don't really like this as-is because it pins a specific (dev!) version.
In a super ideal world, our target platforms would distribute stem
packages that have the Timeout exception added. But that won't happen
for a while. In an ideal world, stem will have hit 1.7.0 with the Timeout
exception and we could require at least that.

Maybe this isn't so bad though? Anyway, I gotta get these Travis tests to
pass!

GH: ref #162

Not currently properly checking that stem is a new enough version.
It needs to be 'git clone'd and installed manually ...

Added in [0] and small fix in [1]

[0]: https://gitweb.torproject.org/stem.git/commit/stem?id=8a065f42952c9dc9762eaebe4d3fa48210783998
[1]: https://gitweb.torproject.org/stem.git/commit/stem?id=60f034ad8b9c3aa48e7e2ecb0a2e159b6ed5bc71

GH: closes #157

There was no such thing as a session.timeout, so it was being ignored.
The timeout has to be set on each request, so add helper funcs to always
add a timeout value.