Fix strict-ssl detection.

When `strict-ssl` is set to a truthy value, npm always turns the
environment variable into the string `true`, when the value is falsy, npm
always sets it to a blank string.  This fixes strict-ssl detection by
always comparing the value of npm_config_strict_ssl to the string `"true"`

npm/install.js

@@ -36,7 +36,7 @@ if (installedVersion === version && fs.existsSync(path.join(__dirname, paths[pla
 }
 
 // downloads if not cached
-download({version: version, platform: process.env.npm_config_platform, arch: process.env.npm_config_arch, strictSSL: process.env.npm_config_strict_ssl}, extractFile)
+download({version: version, platform: process.env.npm_config_platform, arch: process.env.npm_config_arch, strictSSL: process.env.npm_config_strict_ssl === 'true'}, extractFile)
 
 // unzips and makes path.txt point at the correct executable
 function extractFile (err, zipPath) {