remove exception handling for cunn

lib/portable.lua

@@ -1,16 +1,2 @@
 require 'nn'
-
-local function load_cuda()
-   require 'cunn'
-end
-if pcall(load_cuda) then
-   require 'cunn'
-else
-   --[[ TODO: fakecuda does not work.
-      
-   io.stderr:write("use FakeCUDA; if you have NVIDIA GPU, Please install cutorch and cunn. FakeCuda will be extremely slow.\n")
-   require 'torch'
-   require 'nn'
-   require('fakecuda').init(true)
-   --]]
-end
+require 'cunn'