Add a generated header for compiled JS.

Add a // Generated by LiveScript 1.x.x Header to compiled JS.

This option is default on when compile LiveScript .

But If you combined with --print  (print result to stdout) , that will disable to generated header.
So if you want RAW compiled javascript output, you can using lsc -cp aaa.ls > aaa.js  .


Ref: #308

Signed-off-by: Rack Lin <racklin@gmail.com>