Adding server.call/pcall option to LUA scripting. (#136)

[parthpatel]

This commit does not remove redis.call/pcall just yet. It also does not rename Redis in error messages such as "Please specify at least one argument for this redis lib call". This allows users to maintain full backwards compatibility while introducing an option to use server.call for new code.

I verified that the unit tests pass. Also manually verified that the redis-server responds to server.call invocations within lua scripting.

[ok]: EVAL - is Lua able to call Redis API? (0 ms)
[ok]: EVAL - is Lua able to call Server API? (1 ms)
[ok]: EVAL - No arguments to redis.call/pcall is considered an error (0 ms)
[ok]: EVAL - No arguments to server.call/pcall is considered an error (1 ms)