also add check and recheck targets that
run DTX_TEST_PROCS many tests in parallel
and re-run only failed tests accord.

see http://clang.llvm.org/extra/clang-tidy/

`add_format` now only takes one argument: a directory that is used
the base dir for recursive globbing files into clang-format
Usages of the macros are adjusted accordingly. It's still possible to
use it multiple times in a project, if one for whatever reason
does not wnat to throw it at the source root. Only one `format`
target will be generated either way, with one subtarget per
`add_format` invocation.

This reverts commit 58048183.
clang-format 3.7 hard fails with unkown config keys present
and since that is now our only target this needed to be
reverted

this closes #10

clang format discovery is improved a lot by using cmake
builtins, allowing us to very easily target a specific
version only.

This is one half of #10

To avoid competing initializiations it has become
necessary to remove the init object from the
threading manager. Library users wanting full
control will need to provide their own now.

Note TBB will create a default init object if
necessary, this defaults to hardware_concurrency many threads.
Which is what we defaulted the init in threadmanage to as well.

Previously FileBuffer was actually buffering to file _and_ `cout`
at the same time.
This is behaviour is now split, with common functionality
in OstreamBuffer. The old behviour is kept by using
a new DualLogStream in the actual logger. This uses the
extensible CombinedBuffer that can be used as a meta container
for any SuspendableStrBuffer.

Float cmp tests for integer, fixes #15 

also add tests for std::size_t

mainly this pulls up variable definitions into the fixture ctor
it also disambiguates the used DEFAULT_EPSILON

this is an API breaking change as an additional param is added to
`ValidationInterface::msg` and the ostream inserter for validation
objects necessarily removed

this automagically handles all compares for vector types too

- bracket etc placement is not whitespace
- typos
- include guards