Reward be more intelligent, related issue #280

[jiangtj]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines.
• Tests for the changes have been added (for bug fixes / features).
  • Muse | Mist have been tested.
  • Pisces | Gemini have been tested.
• Docs have been added / updated (for bug fixes / features).

PR Type

What kind of change does this PR introduce?

• Bugfix.
• Feature.
• Code style update (formatting, local variables).
• Refactoring (no functional changes, no api changes).
• Build related changes.
• CI related changes.
• Documentation content changes.
• Other... Please describe:

What is the current behavior?

The reward setting is only a switch
Issue Number(s): #280

What is the new behavior?

The reward setting is a switch that reward is or isn't displayed by default.
And you can show or hide one article specially through add page variable reward: true/false.

• My blog articles are opened by default, look https://jiangtj.gitlab.io/
• And one article is closed, https://jiangtj.gitlab.io/2017/08/08/tool/

How to use?

In NexT _config.yml:

# Reward
# If true, reward would be displayed in every article by default.
# And you can show or hide one article specially through add page variable `reward: true/false`.
reward:
  enable: false
  #comment: Donate comment here
  #wechatpay: /images/wechatpay.jpg
  #alipay: /images/alipay.jpg
  #bitcoin: /images/bitcoin.png

Or special config in .md

---
title: title-name
date: 2018-11-05
...
reward: true/false
---

Does this PR introduce a breaking change?

• Yes.
• No.

Breaking change