Add more test configurations.

Merge pull request #12 from sheredom/make_printfs_better ...

Make printfs better

MR: add .clang-format file to stop clang-format always breaking windows builds by reordering includes.

Output errors on clang/gcc.

Remove printf0 printf1 printf2 macros and just suppress the clang warning.

Merge pull request #11 from sheredom/big_shakeup ...

Big shakeup of utest.h

MR: Gurgh another issue with 32bit this time.

MR: VS14 update 2 has an annoying printf bug.@

MR: Hopeful fix for VS14

MR: Remove spurious pragma warning push.@

MR: Remove VS9 testing for now, spurious failures. Make ASSERT not doubly evaluate condition.

MR: lets not use stdint.h on Windows because old MSVC doesn't have it (and we only want two types from it anyway).

MR: CMake doesn't like VS9 not having the 2008, so change the appveyor accordingly.

MR: Fix windows builds.

Enable old VS too.

Use c89 mode for gcc/clang.

MR: CMake fails if you use clang for c and gcc for c++.

MR: Clang complains about varargs macros pre c++11.

MR: can't use snprintf (only for 2013 onwards), use _snprintf_s instead.

MR: Hopeful fix for MSVC.

MR: hopeful fix for gcc error.

MR: can't use strncmp because recursive macro hell on travis-ci.

MR: use clangs __has_warning to check if the warning exists before supressing it.

MR: need to use __STDC_FORMAT_MACROS on linux.

MR: null terminator space was missing, whoops.

MR: fix linux issue.

Big shake-up of utest.h. ...

I've added --output, fixture and indexed testcases, fleshed out the README.md, and generally just finished up utest.h some more!

And lets not revert the filter technology in the process!

Add two more fixtures to re-use a fixture.

Add fixtures. ...

Fixtures allow us to use a struct in combination with UTEST_F_SETUP and UTEST_F_TEARDOWN. This means we can instantiate a struct across multiple fixtures and use shared state between them all. The struct's fixture state is re-initialized for every testcase.