Qemu integration of the test suite

This is primarily intended to provide testing of Thumb-specific code within Travis CI as well as if anyone else want to run it locally. As discussed in #515, the idea of Qemu port had been mostly to build upon for testing purposes. This is currently agains an emulated Cortex-M3 core, however in the near future it can extended to support M0, M0+ as well M4 (work in progress exists in [sushihangover/qemu](https://github.com/sushihangover/qemu)).

It's probably true that most of the code base can be covered running uPy natively on a POSIX system, however we do have the tiny bit of assembly code. There may exist bugs related to endianness and type aliases, let alone potential standard library or compiler bugs or even architecture-specific optimisations.

This could also incorporate lwIP (or other TCP/IP stack) integration as well as SDIO+FATFS drivers.

The solution to inline the test cases was chose due to simplicity. It could alternatively be implemented in a number of different way (see [#515](https://github.com/micropython/micropython/pull/515#issuecomment-41329414)), but this looked the simplest.

Inclusion of tinytest was just to avoid writing boilerplate code for counting failed tests and other utility functions. Currently only a few functions are used, however this could be extended. Checking in the code instead of using submodule was a personal preference, but if people do want the pain of submodules, this can provided. This particular framework is also pretty good if one desires to run unit test on target. The approach with scripts being inlined is probably not quite suited for the size of memory an MCU has, but the tinytest itself should be good, if lower-level C code is to be unit tested.