Update .travis.yml

Check that the bare-arm, stmhal and unix-cpy ports at least remain compilable, even if we can only actually run tests against the unix port.
Merge remote-tracking branch 'upstream/master' into patch-1

Conflicts:
	.travis.yml
Fixed Travis-CI Build Status Link in README.md
travis: build unix targets first

because @pfalcon says so
travis: only build unix with gcc-4.7
Move entry_table to separated header file.
Merge pull request #490 from redteam316/master

Fixed Travis-CI Build Status Link in README.md
travis: On fail, cd to tests directory before diffing.
travis: Debugging failing tests.
travis: More tests debugging.
stmhal: Wrap skin-named-usarts in PYBV10 #if.
travis: More tests output debugging.
travis: Continue to debug tests output.

Seems that any commands in after_failure do not have stdout...
travis: Diff output, hopefully this works.
tests: Disable memoryerror.py test, since it fails on travis.

Would be good to test this, but need to find a way to optionally not
running it when on travis.
py: Add hex builtin function.

A one-liner, added especially for @pfalcon :)
py: Fix builtin hex to print prefix.

I was too hasty.  Still a one-liner though.
travis: Move diffing back to after_failure command.

Need to click on icon at right to see the output.
Rename header file.
Merge pull request #493 from aitjcize/patch

Move entry_table to separated header file.