Add istanbul to dev-deps, for test coverage reports

gulpfile.js

@@ -128,7 +128,7 @@ gulp.task('plato', shell.task(['plato -d report -r -l .jshintrc -t bitcore lib']
 
 gulp.task('jsdoc', shell.task(['jsdoc -c .jsdoc.conf lib']));
 
-gulp.task('coverage', shell.task(['istanbul cover _mocha -- --recursive']));
+gulp.task('coverage', shell.task(['node_modules/.bin/./istanbul cover node_modules/.bin/_mocha -- --recursive']));
 
 gulp.task('coveralls', ['coverage'], function() {
   gulp.src('coverage/lcov.info').pipe(coveralls());

package.json

@@ -100,6 +100,7 @@
     "gulp-mocha": "^2.0.0",
     "gulp-shell": "^0.2.10",
     "ink-docstrap": "git://github.com/bitpay/bitcore-jsdoctemplates.git",
+    "istanbul": "^0.3.5",
     "karma": "^0.12.28",
     "karma-firefox-launcher": "^0.1.3",
     "karma-mocha": "^0.1.9",