Add Travis CI configuration to build and test Wren on both Linux and macOS, for both 32-bit and 64-bit architectures, with and without WREN_NAN_TAGGING defined. Introduce `ci_32` and `ci_64` make targets that build debug/release and C/C++ variants, then run the test suite against each binary using a suffix parameter. Update `util/test.py` with argparse to accept `--suffix` and `suite` arguments, increase test timeout from 2 to 5 seconds, and fix handle leak in `test/api/slots.c` by moving `wrenReleaseHandle` after the conditional block. Replace `fpclassify`/`signbit` checks for infinity/nan in `wrenNumToString` to avoid GCC overflow warnings on 32-bit, double-cast `double` to `uint32_t` in `num_bitwiseNot` to prevent undefined behavior, and relax floating-point comparisons in `test/core/number/sin.wren` and `cos.wren` to use absolute tolerance. Comment out hex literals larger than `0x1000000` in `example/syntax.wren` since they exceed 32-bit range, and bump libuv from v1.8.0 to v1.10.0 for 32-bit build fixes.
- Delete wren_io.c, wren_io.h, and io.wren source files
- Remove multi-arity print overloads and IO.read/IO.time methods
- Add System class with print, printAll, write, writeAll methods to core.wren
- Update all documentation examples and README to use System.print instead of IO.print
