title: gulp-minify causes breaking sass task
body: <p>I'm trying to write modular Ionic1.x app. I was going to compile &amp; concat &amp; minify javascript and scss files.</p>
  
  <p>However, when I use minify function at compress task, I got following error on sass task. </p>
  
  <pre><code>Muhammets-MacBook-Pro-3:x-app MmtBkn$ gulp
  [01:00:29] Using gulpfile ~/Documents/Projects/x-app/gulpfile.js
  [01:00:29] Starting 'sass'...
  [01:00:29] Starting 'compress'...
  [01:00:29] Finished 'compress' after 3.22 ms
  [01:00:29] Starting 'watch'...
  [01:00:29] Finished 'watch' after 9.32 ms
  
  &lt;--- Last few GCs ---&gt;
  
    181117 ms: Scavenge 1386.3 (1457.2) -&gt; 1386.3 (1457.2) MB, 0.3 / 0 ms (+ 0.7 ms in 1 steps since last GC) [allocation failure] [incremental marking delaying mark-sweep].
    182315 ms: Mark-sweep 1386.3 (1457.2) -&gt; 1261.2 (1457.2) MB, 1197.8 / 0 ms (+ 1.6 ms in 2 steps since start of marking, biggest step 0.9 ms) [last resort gc].
    183817 ms: Mark-sweep 1261.2 (1457.2) -&gt; 1261.2 (1457.2) MB, 1501.7 / 0 ms [last resort gc].
  
  
  &lt;--- JS stacktrace ---&gt;
  
  ==== JS stack trace =========================================
  
  Security context: 0x2e01223e3ac1 &lt;JS Object&gt;
      2: /* anonymous */(aka /* anonymous */) [0x2e0122304189 &lt;undefined&gt;:~5007] [pc=0x39378c3457ff] (this=0x2e0122304189 &lt;undefined&gt;,self=0x531caddf789 &lt;an AST_Number with map 0x29489836add9&gt;,output=0x38677a93b4f1 &lt;an Object with map 0x29489836c959&gt;)
      3: doit(aka doit) [0x2e0122304189 &lt;undefined&gt;:4197] [pc=0x39378c24c878] (this=0x2e0122304189 &lt;undefined&gt;)
      4: print [0x2e0122304189 &lt;undefin...
  
  FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - process out of memory
  Abort trap: 6
  </code></pre>
  
  <p>Yes, I don't know how or why but, when I comment minify lines which is at compress task, sass works well. I tried to re install packages, setup new project etc. nothing changes. Here is gulpfile.js</p>
  
  <pre><code>var gulp = require('gulp');
  var gutil = require('gulp-util');
  var bower = require('bower');
  var concat = require('gulp-concat');
  var sass = require('gulp-sass');
  var minifyCss = require('gulp-minify-css');
  var rename = require('gulp-rename');
  var sh = require('shelljs');
  var minify = require('gulp-minify');
  
  
  var paths = {
    sass: ['./scss/**/*.scss']
  };
  
  gulp.task('serve:before', ['default','watch']);
  
  gulp.task('default', ['sass','compress','watch']);
  
  gulp.task('sass', function(done) {
    gulp.src(['./scss/ionic.app.scss','./www/app/**/*.scss'])
      .pipe(sass())
      .on('error', sass.logError)
      .pipe(concat('app.css'))
      .pipe(minifyCss())
      .pipe(gulp.dest('./www'))
      .on('end', done);
  });
  
  gulp.task('compress', function() {
    gulp.src('./www/**/*.js')
      .pipe(concat('app.js'))
      .pipe(minify({
        ext:{
          src:'-debug.js',
          min:'.js'
        },
        exclude: ['./www/lib'],
        ignoreFiles: ['.combo.js', '-min.js']
      }))
      .pipe(gulp.dest('./www'))
  });
  </code></pre>
  
  <p>My OS version is OS X El Capitan with more than enough memory.
  Package versions are</p>
  
  <pre><code>"gulp": "^3.5.6",
  "gulp-sass": "^2.0.4",
  "gulp-concat": "^2.2.0",
  "gulp-minify-css": "^0.3.0",
  "gulp-minify":"0.0.14", 
  "gulp-rename": "^1.2.0"
  </code></pre>
  
  <p>Any idea? Thank you.</p>