Rebuild rotom to v2

[xgzlucario]

rotom 更新至 v2 版本，由原先的嵌入式 db 重写为 tiny redis server, 兼容 Redis RESP 协议。
具体特性如下：

1. 基于 single epoll server 实现 IO 多路复用
2. 兼容 RESP 协议，目前支持 ping set get hset hget hgetall
3. AOF 支持

更多详情查看 README

[codecov]

Codecov Report

Attention: Patch coverage is 64.74576% with 104 lines in your changes missing coverage. Please review.

Project coverage is 62.55%. Comparing base (b19d4b5) to head (b801d29).

Files	Patch %	Lines
rotom.go	52.27%	31 Missing and 11 partials ⚠️
handler.go	71.11%	21 Missing and 5 partials ⚠️
main.go	0.00%	18 Missing ⚠️
aof.go	0.00%	14 Missing ⚠️
utils.go	60.00%	1 Missing and 1 partial ⚠️
config.go	0.00%	1 Missing ⚠️
resp.go	98.68%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master      #39       +/-   ##
===========================================
- Coverage   98.53%   62.55%   -35.98%     
===========================================
  Files           4        9        +5     
  Lines         613      430      -183     
===========================================
- Hits          604      269      -335     
- Misses          5      139      +134     
- Partials        4       22       +18     

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