Update microtime dependency

[nwinch]

I'm getting errors when installing with Node 0.11.x.

npm ERR! Darwin 13.4.0
npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "install" "sifter" "--save"
npm ERR! node v0.11.14
npm ERR! npm v2.0.0
npm ERR! code ELIFECYCLE
npm ERR! microtime@0.5.1 install: node-gyp rebuild
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the microtime@0.5.1 install script.
npm ERR! This is most likely a problem with the microtime package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR! node-gyp rebuild
npm ERR! You can get their info via:
npm ERR! npm owner ls microtime
npm ERR! There is likely additional logging output above.

Could you add support for a later version of microtime? The author seems to have added support for 0.11.x:
wadey/node-microtime#19

[damianbaar]

+1

[brianreavis]

Updated: 0.4.1