Update nan to build on newer node 10.x

[tlbdk]

Build fails on newer node versions, see: nodejs/nan#763 .

> node-expat@2.3.16 install /Users/f736trbe/git/tlb/node-xmlexact/node_modules/node-expat
> node-gyp rebuild

  CC(target) Release/obj.target/expat/deps/libexpat/lib/xmlparse.o
  CC(target) Release/obj.target/expat/deps/libexpat/lib/xmltok.o
  CC(target) Release/obj.target/expat/deps/libexpat/lib/xmlrole.o
  LIBTOOL-STATIC Release/libexpat.a
  CXX(target) Release/obj.target/node_expat/node-expat.o
In file included from ../node-expat.cc:1:
In file included from ../../nan/nan.h:192:
../../nan/nan_maybe_43_inl.h:112:15: error: no member named 'ForceSet' in 'v8::Object'
  return obj->ForceSet(isolate->GetCurrentContext(), key, value, attribs);
...
4 warnings and 1 error generated.
make: *** [Release/obj.target/node_expat/node-expat.o] Error 1
gyp ERR! build error
gyp ERR! stack Error: `make` failed with exit code: 2
gyp ERR! stack     at ChildProcess.onExit (/usr/local/lib/node_modules/npm/node_modules/node-gyp/lib/build.js:258:23)
gyp ERR! stack     at ChildProcess.emit (events.js:182:13)
gyp ERR! stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:237:12)
gyp ERR! System Darwin 17.7.0
gyp ERR! command "/usr/local/Cellar/node/10.5.0_1/bin/node" "/usr/local/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "rebuild"
gyp ERR! cwd /Users/f736trbe/git/tlb/node-xmlexact/node_modules/node-expat
gyp ERR! node -v v10.5.0
gyp ERR! node-gyp -v v3.6.2
gyp ERR! not ok
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! node-expat@2.3.16 install: `node-gyp rebuild`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the node-expat@2.3.16 install script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/f736trbe/.npm/_logs/2018-08-06T17_11_05_001Z-debug.log

[3z3qu13l]

@astro could you take a look on that.
Node10 LTS is comming soon and a lot of people will want to use it.
Thanks @tlbdk

[astro]

Thank you.