Specify actual files for tests.

Apparently, automake's test driver doesn't like directories as targets.
There are a couple of minor hacks here, which I'll fix eventually.
Outright replace ruby script with shell script.

At least I know that one will work. Besides, with the file name already
specified in the Makefile.am, it doesn't really need to do very much. No
complicated file globbing (not that that's hard) required.
Change test-driver from symlink to the actual file.
Require automake 1.11 and parallel tests.

This seems to be the cause of the test failures on Travis CI, as it
doesn't have automake 1.13. That's the version where parallel tests
became the default and I guess the serial test driver doesn't work the
same way.
Tweak Travis script.

* Enable parallel build and testing.
* Enable output of test failure information since we can't really
  examine the log file on Travis.
Enable portability checks for automake.
Specify test extensions for automake.
Remove default Makefile as git is annoying with it.
Mark TODO specs as expected failures.
Add a better script for the benchmark tests.
Enable extended tests on Travis-CI.

They don't really take that long anyway.