Increment m_scriptEnvIndex limit
Use Lua stack index -1 in popUserdata
Use param instead of template for Lua get* args
Use pushBoolean instead of lua_pushboolean

lua_pushboolean takes an int as second argument, causing an implicit
cast from bool to int. By using pushBoolean we can pass a C++ bool and
let the pushBoolean function check whether it's true/false and then pass
1 or 0 as int to lua_pushboolean.
Fix linking errors
Fix linking errors again

Travis build was still failing