Fix incorrect use of coxpcall

require "coxpcall" returns a table
Fix backward compatibility with Lua 5.1 - coxpcall required...

Resolves "attempt to yield across metamethod/C-call boundary" errors when running Wsapi apps such as Orbit on Lua < 5.2
Merge pull request #30 from kognix/master

Wsapi 1.6 breaks Orbit and potentially other Lua 5.1 apps...