testsuite: add src/common/libtap

Brought in tap.c and tap.h from https://github.com/zorgnax/libtap
Grabbed the latest master - last modified 2014-05-15.
testsuite: convert nodeset unit tests to TAP

Create test/nodeset as a check_PROGRAMS target.
This is nodeset.c compiled with -DTEST_MAIN.
nodeset_selftest() was converted to a conditionally compiled main().
testsuite: run unit tests from their Makefile.am
testsuite: build libtap as a check_LTLIBRARY
Merge pull request #43 from garlick/libtap

import libtap, convert nodeset tests to TAP
testsuite: lua: move unit test sources to new name

In preparation for rewrite of unit tests, move tests to a new name.
testsuite: add lua-TestMore to src/bindings/lua/Test

Add lua-TestMore Lua unit testing framework from

 https://github.com/fperrad/lua-TestMore/
testsuite: rewrite lua unit test code in lua-TestMore

Use lua-TestMore in preference to lunit. TestMore generates
TAP output so will be compatible with our other testsuite tests.

Additionally, the tests can be run by make directly, so we fix
the issue with incompatible 'make check' with differring automake
versions.

Fixes #36.
testsuite: lua: remove lunit

The `lunit` test driver for lua unit tests is no longer used.
Merge pull request #44 from grondo/lua-unit-tests-update

Update Lua unit tests to lua-TestMore (with TAP output)