Addresses issue #104.

Define buffer and stream protocols, and other starting bits of io.* framework, with io.FileIO-like implementation for Unix

Update teemsy/Makefile to use py.mk

Update stm/Makeile to use OBJCOPY and SIZE macros

I also fixed main.c to compile with the new str lexer

While updating the teensy Makfile, I noticed that the stm Makefile
was using calling arm-none-eabi-objcopy and size rather than
$(OBJCOPY) and $(SIZE), so I added these 2 for consistency.

Note: only read/write/close methods are defined so far, and class
is not exposed (use open() factory function, as usual).

These can be used for any object which implements stream protocol
(mp_stream_p_t).

Stream protocol is abstraction of serial I/O. Buffer protocol is
abstraction of random-access I/O. These protocols are defined down
to C level, to allow generic, while still efficient algorithms
to be coded in C (like, buffered transfer between 2 stream objects,
saving/loading of buffer object to/from stream, etc). (Note that CPython
define buffer protocol on C level, but apparently not stream protocol).

Use LSI OSC for RTC clock when LSE is not detected

Updated teensy to use common code from stm directory.

* Fix rtc_init to use LSI for RTC clock source when LSE is not detected.

Updated mconfigport.h to enable GC

Dictionary features that don't involve views or classmethods. First part of issue #99.

Added 0 to the list of primes. Funky primes, these.

* Fix LED pin enum, first one should start at 1
* Fix LED initialization typo

A more python-style list.sort. And keyword arguments.