Make microtime a devDependency again

[pirelenito]

Placing it in the optionalDependencies (8423738) makes it being installed on consumers of this library, which shouldn't be required.

Is there another reason?

Thanks for the amazing work on this library.

[pirelenito]

If you think it is fine, I can prepare a PR.

[ticolucci]

On yarn install of a project using webpack I got an error.
Big errors are scary =P
(even when there's a message that it's ok to ignore it)

Console:

[4/4] Building fresh packages...
warning Error running install script for optional dependency: "/opt/le_project/client/node_modules/microtime: Command failed.\nExit code: 1\nCommand: sh\nArguments: -c node-gyp rebuild\nDirectory: /opt/le_project/client/node_modules/microtime\nOutput:\ngyp info it worked if it ends with ok\ngyp info using [email protected]\ngyp info using [email protected] | linux | x64\ngyp http GET https://nodejs.org/download/release/v7.8.0/node-v7.8.0-headers.tar.gz\ngyp http 200 https://nodejs.org/download/release/v7.8.0/node-v7.8.0-headers.tar.gz\ngyp http GET https://nodejs.org/download/release/v7.8.0/SHASUMS256.txt\ngyp http 200 https://nodejs.org/download/release/v7.8.0/SHASUMS256.txt\ngyp info spawn /usr/bin/python2\ngyp info spawn args [ '/usr/share/yarn/node_modules/node-gyp/gyp/gyp_main.py',\ngyp info spawn args 'binding.gyp',\ngyp info spawn args '-f',\ngyp info spawn args 'make',\ngyp info spawn args '-I',\ngyp info spawn args '/opt/le_project/client/node_modules/microtime/build/config.gypi',\ngyp info spawn args '-I',\ngyp info spawn args '/usr/share/yarn/node_modules/node-gyp/addon.gypi',\ngyp info spawn args '-I',\ngyp info spawn args '/opt/le_project/.node-gyp/7.8.0/include/node/common.gypi',\ngyp info spawn args '-Dlibrary=shared_library',\ngyp info spawn args '-Dvisibility=default',\ngyp info spawn args '-Dnode_root_dir=/opt/le_project/.node-gyp/7.8.0',\ngyp info spawn args '-Dnode_gyp_dir=/usr/share/yarn/node_modules/node-gyp',\ngyp info spawn args '-Dnode_lib_file=node.lib',\ngyp info spawn args '-Dmodule_root_dir=/opt/le_project/client/node_modules/microtime',\ngyp info spawn args '-Dnode_engine=v8',\ngyp info spawn args '--depth=.',\ngyp info spawn args '--no-parallel',\ngyp info spawn args '--generator-output',\ngyp info spawn args 'build',\ngyp info spawn args '-Goutput_dir=.' ]\ngyp ERR! build error \ngyp ERR! stack Error: not found: make\ngyp ERR! stack at getNotFoundError (/usr/share/yarn/node_modules/which/which.js:13:12)\ngyp ERR! stack at F (/usr/share/yarn/node_modules/which/which.js:68:19)\ngyp ERR! stack at E (/usr/share/yarn/node_modules/which/which.js:80:29)\ngyp ERR! stack at /usr/share/yarn/node_modules/which/which.js:89:16\ngyp ERR! stack at /usr/share/yarn/node_modules/isexe/index.js:42:5\ngyp ERR! stack at /usr/share/yarn/node_modules/isexe/mode.js:8:5\ngyp ERR! stack at FSReqWrap.oncomplete (fs.js:114:15)\ngyp ERR! System Linux 4.9.13-moby\ngyp ERR! command "/usr/local/bin/node" "/usr/share/yarn/node_modules/node-gyp/bin/node-gyp.js" "rebuild"\ngyp ERR! cwd /opt/le_project/client/node_modules/microtime\ngyp ERR! node -v v7.8.0\ngyp ERR! node-gyp -v v3.6.1\ngyp ERR! not ok"
info This module is OPTIONAL, you can safely ignore this error

[calvinmetcalf]

and done