fix compatibility with Node 13

[chrmoritz]

This PR should make lzma-native compatible with Node.js 13 by fixing compilation errors (due to recent V8 changes) like:

../src/index-parser.cpp:443:12: error: no matching member function for call to 'Set'
  exports->Set(NewString("IndexParser"), Nan::New<Function>(constructor));
  ~~~~~~~~~^~~
/Users/chrmoritz/Library/Caches/node-gyp/13.1.0/include/node/v8.h:3424:37: note: candidate function not viable: requires 3 arguments, but 2 were provided
  V8_WARN_UNUSED_RESULT Maybe<bool> Set(Local<Context> context,
                                    ^
/Users/chrmoritz/Library/Caches/node-gyp/13.1.0/include/node/v8.h:3427:37: note: candidate function not viable: requires 3 arguments, but 2 were provided
  V8_WARN_UNUSED_RESULT Maybe<bool> Set(Local<Context> context, uint32_t index,

This also adds Node.js 13 to the CI and removes the now EOL Node.js 11 from it.

[addaleax]

Thanks, published in v4.0.6!