Tentative fix for #135

As promise, here comes the patch.
In first place, sorry if I deliberately went too far in maybe taking some design choices (but after all we are here to discuss them :) )

The idea is pretty simple: I've customised the `Options` record to allow a `[OptDesc (OptResult -> OptResult)]` so that the user can use base's `GetOpt` to inject his own options. This imho has several advantages:

* We reuse a base library, thus we don't rely on third party stuff
* We solve all our problems, because this way the user has full control over his own flags
* I might have some nice real world use.

I've adapted yesterday's code to use the patched code, this is the gist :

``` haskell
options :: [OptDescr (OptResult -> OptResult)]
options = [
    Option "e" ["environment"] (ReqArg (const id) "ENVIRONMENT") "Which environment to use"
  ]

hspec' :: Spec -> IO ()
hspec' = hspecWithUserOptions options

main :: IO ()
main = do
  [_, env] <- getArgs
  withFreshDB env "news" (hspec' newsSpec)
  hspec' $ do
    authSpec
    cacheSpec
```

What is nice is that we get the description for the flag for free:

```
OPTIONS
                  --help                            display this help and exit
  -m PATTERN      --match=PATTERN                   only run examples that match given PATTERN
                  --color                           colorize the output
                  --no-color                        do not colorize the output
  -f FORMATTER    --format=FORMATTER                use a custom formatter; this can be one of:
                                                       specdoc
                                                       progress
                                                       failed-examples
                                                       silent
  -o FILE         --out=FILE                        write output to a file instead of STDOUT
                  --depth=N                         maximum depth of generated test values for
                                                    SmallCheck properties
  -a N            --qc-max-success=N                maximum number of successful tests before a
                                                    QuickCheck property succeeds
                  --qc-max-size=N                   size to use for the biggest test cases
                  --qc-max-discard=N                maximum number of discarded tests per
                                                    successful test before giving up
                  --seed=N                          used seed for QuickCheck properties
                  --print-cpu-time                  include used CPU time in summary
                  --dry-run                         pretend that everything passed; don't verify
                                                    anything
                  --fail-fast                       abort on first failure
  -r              --rerun                           rerun all examples that failed in the
                                                    previously test run (only works in GHCi)
                  --maximum-generated-tests=NUMBER  how many automated tests something like QuickCheck should try, by default
                  --html                            produce HTML output
  -v              --verbose                         do not suppress output to stdout when evaluating examples
  -e ENVIRONMENT  --environment=ENVIRONMENT         Which environment to use
```

I've summarised below the most prominent changes, feel free to comment over. Some might be suboptimal, let's crack on them together :)

* Result from `Test.Hspec.Options` has been renamed to `OptResult`. This was because it now needs to be exported, and it was conflicting with `Types.Result`
* The help now shows also the `undocumentedOptions`. Decide whether this is good or not
* Options module now needs to be exposed, unless we want to keep it private but put the burden on the user which has to import `System.Console.GetOpt`. I don't mind which of the two we choose.
* Some refactoring, including outsourcing some long string into proper let bindings and some miscellanea refactoring, as suggested by the linter.

Should be all!
Ah!

1 Test is currently failing, but I can't figure out if it's my patch, but it seems marginal anyway:

```
1) Test.Hspec.Runner.hspec, with --help, constrains lines to 80 characters
predicate failed on: ["Usage: spec [OPTION]...","","OPTIONS","                --help                            display this help and exit","
  -m PATTERN    --match=PATTERN                   only run examples that match given PATTERN","                --color
    colorize the output","                --no-color                        do not colorize the output","  -f FORMATTER  --format=FORMATTER
              use a custom formatter; this can be one of:","                                                     specdoc","
                                   progress","                                                     failed-examples","
                             silent","  -o FILE       --out=FILE                        write output to a file instead of STDOUT","
      --depth=N                         maximum depth of generated test values for","                                                  SmallC
heck properties","  -a N          --qc-max-success=N                maximum number of successful tests before a","
                       QuickCheck property succeeds","                --qc-max-size=N                   size to use for the biggest test case
s","                --qc-max-discard=N                maximum number of discarded tests per","
   successful test before giving up","                --seed=N                          used seed for QuickCheck properties","
 --print-cpu-time                  include used CPU time in summary","                --dry-run                         pretend that everythi
ng passed; don't verify","                                                  anything","                --fail-fast                       abor
t on first failure","  -r            --rerun                           rerun all examples that failed in the","
                    previously test run (only works in GHCi)","                --maximum-generated-tests=NUMBER  how many automated tests som
ething like QuickCheck should try, by default","                --html                            produce HTML output","  -v            --ver
bose                         do not suppress output to stdout when evaluating examples"]

Randomized with seed 4611685480699978188
```