create sourcemap and rig up remap-istanbul

gobblefile.js

@@ -8,7 +8,8 @@ var node = src
 		entry: 'rollup.js',
 		dest: 'rollup.js',
 		format: 'cjs',
-		external: [ 'sander', 'acorn' ]
+		external: [ 'sander', 'acorn' ],
+		sourceMap: true
 	})
 	.transform( 'babel' );
 

package.json

@@ -11,8 +11,9 @@
     "pretest": "npm run build",
     "test": "mocha",
     "pretest-coverage": "npm run build",
-    "test-coverage": "istanbul cover --report cobertura node_modules/.bin/_mocha -- -u exports -R spec test/test.js",
-    "ci": "npm run test-coverage && codecov < coverage/cobertura-coverage.xml",
+    "test-coverage": "istanbul cover --report json node_modules/.bin/_mocha -- -u exports -R spec test/test.js",
+    "posttest-coverage": "remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped.json -b dist",
+    "ci": "npm run test-coverage && codecov < coverage/coverage-remapped.json",
     "build": "gobble build -f dist",
     "prepublish": "npm test",
     "lint": "eslint src"