Fix: Avoid marking --tasks-json as string to catch booleans (closes #41)

Author: phated

lib/shared/cliOptions.js

@@ -53,7 +53,6 @@ module.exports = {
       'Print a plaintext list of tasks for the loaded gulpfile.'),
   },
   'tasks-json': {
-    type: 'string',
     desc: chalk.gray(
       'Print the task dependency tree, ' +
       'in JSON format, for the loaded gulpfile.'),