Providing relative paths to Istanbul. now reports actually show up in the reports directory rather than next to my .sol files and css/js references work

lib/app.js

@@ -218,11 +218,12 @@ class App {
     return new Promise((resolve, reject) => {
       try {
         this.coverage.generate(this.events, `${this.workingDir}/contracts`);
+        const newCoverage = App.makeKeysRelative(this.coverage.coverage, this.workingDir);
 
-        const json = JSON.stringify(this.coverage.coverage);
+        const json = JSON.stringify(newCoverage);
         fs.writeFileSync('./coverage.json', json);
 
-        collector.add(this.coverage.coverage);
+        collector.add(newCoverage);
         reporter.add('html');
         reporter.add('lcov');
         reporter.add('text');
@@ -240,6 +241,14 @@ class App {
 
   // ------------------------------------------ Utils ----------------------------------------------
 
+  static makeKeysRelative(map, root) {
+    const newCoverage = {};
+    Object.keys(map).forEach(pathKey => {
+      newCoverage[path.relative(root, pathKey)] = map[pathKey];
+    });
+    return newCoverage;
+  }
+
   /**
    * Allows config to turn logging off (for CI)
    * @param {Boolean} isSilent