Lua bindings enhancements: timer methods, testsuite, and Lua 5.2 support

This pull request builds up to adding Lua 5.2 support. The support is nominal and
has only been briefly tested on Ubuntu 14.04, however, this groundwork allows flux
lua bindings to at least compile and run on later distros with lua5.2 installed by default.

Summary
 - Add missing functionality in lua bindings (timers, `flux_reactor_stop`, `recv_event`, etc)
 - Add a sharness-like testsuite module for lua code under `t/fluxometer.lua`
 - Tests for Lua API bindings (which in turn tests a lot of the underly C APIs)
 - Lua 5.2 support
 - Other fixes required along the way

Ideally this patch series would also enable travis-ci builds with Lua 5.2, but that turns out
to be a huge pain.