Updated dependencies

[adon-at-work]

This PR updates (dev)dependencies to their latest versions except:

• grunt-execute is unmaintained in these two years, and depends on very old packages. this is resolved by replacing it with grunt-exec.
• handlebars 4 is not picked up in this revision, as there involves breaking and syntactical changes. A separate branch https://github.com/yahoo/secure-handlebars/tree/update-to-handlebars-4 is created, some attempts are made, but we'll need help to make it fully compatible.

p.s. this has eliminated the use of graceful-fs@3.x

@neraliu @maditya

[yahoocla]

CLA is valid!