Simplify use of binaries off a local artifactory

Allow installing a package with many dependent packages using node-pre-gyp binaries off the same local artifactory.

Avoid erasing the subpath in the mirror value.

lib/util/versioning.js

@@ -309,7 +309,7 @@ module.exports.evaluate = function(package_json,options,napi_build_version) {
     // support host mirror with npm config `--{module_name}_binary_host_mirror`
     // e.g.: https://github.com/node-inspector/v8-profiler/blob/master/package.json#L25
     // > npm install v8-profiler --profiler_binary_host_mirror=https://npm.taobao.org/mirrors/node-inspector/
-    var host = process.env['npm_config_' + opts.module_name + '_binary_host_mirror'] || package_json.binary.host;
+    var host = process.env.npm_config_binary_host_mirror || process.env['npm_config_' + opts.module_name + '_binary_host_mirror'] || package_json.binary.host;
     opts.host = fix_slashes(eval_template(host,opts));
     opts.module_path = eval_template(package_json.binary.module_path,opts);
     // now we resolve the module_path to ensure it is absolute so that binding.gyp variables work predictably
@@ -322,6 +322,9 @@ module.exports.evaluate = function(package_json,options,napi_build_version) {
     }
     opts.module = path.join(opts.module_path,opts.module_name + '.node');
     opts.remote_path = package_json.binary.remote_path ? drop_double_slashes(fix_slashes(eval_template(package_json.binary.remote_path,opts))) : default_remote_path;
+    if (opts.remote_path.charAt(0) == "/") {
+        opts.remote_path = opts.remote_path.substr(1);
+    }
     var package_name = package_json.binary.package_name ? package_json.binary.package_name : default_package_name;
     opts.package_name = eval_template(package_name,opts);
     opts.staged_tarball = path.join('build/stage',opts.remote_path,opts.package_name);