Tostring tests

Add a bunch of test cases for ToString (esp. vector et al).

I also added a makefile (prior to there being one on master)

My makefile has the nice benefit that it just grabs all the '.cpp' files in the current directory - so adding new test cases doesn't require modification.

On the other hand, it's geared to my build setup (clang/c++11/libc++), so will need modification for folks that use other toolchains.

I think the former (glob *'cpp) is a no-brainer for the SelfTest, but we should probably discuss how to proceed with the env. setup.

As a consequence, you may wish to consider merging the first four commits (the test cases, and .gitignore) - and doing something else with the makefile commit (ba4dda4)

(And there's a generic `StringMaker<std::pair>` embedded in one of my tests - which probably ought to be migrated to `catch_tostring.hpp` unless it's likely to break anything)

Take a look, and let me know how you'd like to restructure this.