node-report not building on Windows due to mktime error

[hhellyer]

I ran a build to test some changes (build 153) and saw compile failures on Windows.

They didn't appear related to my changes so I ran a build using master and Node v6 and saw the same failures:
https://ci.nodejs.org/view/post-mortem/job/nodereport-continuous-integration/154/

(smartos also had failures but they were issues running node not compile failures and I will investigate those separately.)

[hhellyer]

I've raised PR #85 to resolve this.

[rnchamberlain]

Fix landed as 1b62e31

[rnchamberlain]

CI now passing OK on Windows