[WIP] Update test api for 20160226 command set

[Thooms]

No description provided.

[Thooms]

@k-bx @qrilka here is my first shot at rewriting a correct testsuite. I only wrote the tests for the strings, and I'd like to know if all seems correct before writing everything else!
The main goal of having separate tests for all the commands is to prepare the switch to handwritten commands. I'll certainly split the testsuite in separate files in this PR, too.

[qrilka]

@Thooms have you seen build failures on Travis?
e.g. HSTRLEN missing? I don't quite understand how got get Redis version used in Travis but I guess we don't need to enable by default all of the tests and use commands existing from some particular version. Probably that one is from Ubuntu Trusty which seems to have 2.8.4

[qrilka]

It looks that Precise is the default - https://docs.travis-ci.com/user/ci-environment/ so Redis there is even older than I thought.
So it looks like we need not to use standard Redis and use some fresh versions, like 2.8, 3.0 (currently stable) and 3.2 (as we have some commands for it already).
And the test suite should disable tests according to Redis version

[qrilka]

and the tests themselves look good to me, thanks @Thooms

[Thooms]

Yes, I saw the Travis fails, I'll try to fix that, and I'll write the rest of the tests (that'll take some time, don't worry if you don't have update) :)

[qrilka]

@Thooms could you rebase you branch on https://github.com/informatikr/hedis/tree/commands-20160226 ?
I almost have code to run tests according to Redis version but because of haddock codegen change in #62 merge could get not clean

[qrilka]

hi @Thooms - do you still plan to continue this effort?