Replace use of npmlog dependency with console.error (#182)

No change to log message format or level

log.js

@@ -1,13 +1,33 @@
-const log = require('npmlog')
+const levels = {
+  silent: 0,
+  error: 1,
+  warn: 2,
+  notice: 3,
+  http: 4,
+  timing: 5,
+  info: 6,
+  verbose: 7,
+  silly: 8
+}
 
 module.exports = function (rc, env) {
-  log.heading = 'prebuild-install'
+  const level = rc.verbose
+    ? 'verbose'
+    : env.npm_config_loglevel || 'notice'
 
-  if (rc.verbose) {
-    log.level = 'verbose'
-  } else {
-    log.level = env.npm_config_loglevel || 'notice'
+  const logAtLevel = function (messageLevel) {
+    return function (...args) {
+      if (levels[messageLevel] <= levels[level]) {
+        console.error(`prebuild-install ${messageLevel} ${args.join(' ')}`)
+      }
+    }
   }
 
-  return log
+  return {
+    error: logAtLevel('error'),
+    warn: logAtLevel('warn'),
+    http: logAtLevel('http'),
+    info: logAtLevel('info'),
+    level
+  }
 }

package.json

@@ -26,7 +26,6 @@
     "mkdirp-classic": "^0.5.3",
     "napi-build-utils": "^1.0.1",
     "node-abi": "^3.3.0",
-    "npmlog": "^4.0.1",
     "pump": "^3.0.0",
     "rc": "^1.2.7",
     "simple-get": "^4.0.0",