I'm installing NodeBB on CentOS7.0, on the step of "npm install", after waited a long time, it returns an error

npm WARN engine [email protected]: wanted: {"node":">= 4"} (current: {"node":"0.12.7","npm":"2.11.3"})
npm WARN engine [email protected]: wanted: {"node":">=4"} (current: {"node":"0.12.7","npm":"2.11.3"})
npm WARN deprecated [email protected]: wrench.js is deprecated! You should check out fs-extra (https://github.com/jprichardson/node-fs-extra) for any operations you were using wrench for. Thanks for all the usage over the years.
npm WARN deprecated [email protected]: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm WARN deprecated [email protected]: graceful-fs v3.0.0 and before will fail on node releases >= v7.0. Please update to graceful-fs@^4.0.0 as soon as possible. Use 'npm ls graceful-fs' to find it in the tree.
npm WARN engine [email protected]: wanted: {"node":">=4"} (current: {"node":"0.12.7","npm":"2.11.3"})
npm WARN deprecated [email protected]: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm ERR! Linux 3.10.0-123.9.3.el7.x86_64
npm ERR! argv "/root/.nvm/v0.12.7/bin/node" "/root/.nvm/v0.12.7/bin/npm" "install"
npm ERR! node v0.12.7
npm ERR! npm v2.11.3
npm ERR! code ECONNRESET
npm ERR! errno ECONNRESET
npm ERR! syscall read

npm ERR! network read ECONNRESET
npm ERR! network This is most likely not a problem with npm itself
npm ERR! network and is related to network connectivity.
npm ERR! network In most cases you are behind a proxy or have bad network settings.
npm ERR! network
npm ERR! network If you are behind a proxy, please make sure that the
npm ERR! network 'proxy' config is set properly. See: 'npm help config'