Fixes #27, where /usr/bin/type was not found on windows (#28)

Should fix [this
issue](#27) where
/usr/bin/type was not found in order to check for `convert` and `gm`
binaries in $PATH.

lib/cli.js

@@ -17,8 +17,8 @@ commander
     .option('--only-web', 'Only generate Web icons')
     .parse(process.argv);
 
-var inputImage = path.resolve(process.cwd(), commander.args[0]);
-var outputPath = (commander.args[1] &&
+const inputImage = path.resolve(process.cwd(), commander.args[0]);
+let outputPath = (commander.args[1] &&
                   fs.statSync(path.resolve(process.cwd(), commander.args[1])).isDirectory()) ?
                     path.resolve(process.cwd(), commander.args[1]) :
                       process.cwd();

lib/iconerator.js

@@ -5,20 +5,20 @@ var fs = require('fs'),
     gm = require('gm'),
     im = require('imagemagick'),
     async = require('async'),
+    commandExists = require('command-exists'),
     _ = require('underscore'),
-    child_process = require('child_process'),
     config = require(__dirname+'/config');
 
 
 function createWebIconFolders(outputPath) {
     if(!fs.existsSync(path.join(outputPath, config.output.webDir))) {
         fs.mkdirSync(path.join(outputPath, config.output.webDir));
     }
-};
+}
 
 function createAndroidIconFolders(outputPath) {
-    var baseDir = path.join(outputPath, config.output.androidDir);
-    var dirs = [
+    const baseDir = path.join(outputPath, config.output.androidDir);
+    const dirs = [
         '',
         '/res',
         '/res/drawable-ldpi',
@@ -35,29 +35,29 @@ function createAndroidIconFolders(outputPath) {
         '/res/mipmap-xxxhdpi'
     ];
 
-    for(var i = 0; i < dirs.length; i++){
+    for(let i = 0; i < dirs.length; i++){
         if(!fs.existsSync(path.join(baseDir, dirs[i]))) fs.mkdirSync(baseDir + dirs[i]);
     }
-};
+}
 
 function createIOSIconFolders(outputPath) {
     if(!fs.existsSync(path.join(outputPath, config.output.iosDir))) {
         fs.mkdirSync(path.join(outputPath, config.output.iosDir));
     }
-};
+}
 
 exports.checkDependencies = function(cb) {
-    child_process.exec("/usr/bin/type convert", function(err, stdout){
-        if(err || stdout === "") return cb("ImageMagick binary not found");
-        child_process.exec("/usr/bin/type gm", function(err, stdout){
-            if(err || stdout === "") return cb("GraphicsMagick binary not found");
+    commandExists('convert', function(err, convertExists){
+        if(!convertExists) return cb("ImageMagick binary not found");
+        commandExists('gm', function(err, gmExists){
+            if(!gmExists) return cb("GraphicsMagick binary not found");
             cb(null);
         });
-    });
+    })
 };
 
 exports.generateIcons = function(inputImg, outputPath, platform, device, cb) {
-    var iconMeta = config.icons,
+    let iconMeta = config.icons,
     error;
 
     if(!fs.statSync(inputImg).isFile()){
@@ -86,7 +86,7 @@ exports.generateIcons = function(inputImg, outputPath, platform, device, cb) {
 
 
     async.each(iconMeta, function(meta, cb){
-        var outputFile;
+        let outputFile;
         if(meta.platform === 'iOS'){
             outputFile = path.join(outputPath, config.output.iosDir, meta.file_name);
         } else if(meta.platform === 'Android'){
@@ -97,7 +97,7 @@ exports.generateIcons = function(inputImg, outputPath, platform, device, cb) {
             outputFile = path.join(outputPath, config.output.webDir, meta.file_name);
         }
 
-        if(meta.platform == 'Web') {
+        if(meta.platform === 'Web') {
             im.convert([inputImg, '-bordercolor', 'white', '-border', '0', '-alpha', 'off', '-colors', '256', '-resize', meta.width+'x'+meta.height, outputFile], function(err){
                if(err) {
                    console.error("Error generating %s (res: %s) icon: %s:: %s", meta.platform, (meta.resolution || ''), meta.file_name, err);