feat: options function return false, fix default logger

[xc1427]

This PR does several things:

• options function now can return false. This allows the middleware to bail out even if path matching succeeds, which could be helpful if you need complex logic to determine whether to proxy or not.
• Fix the default logger. Because the proxying is done by http-proxy, Getting correct proxied url needs imitating the behavior of http-proxy. The original implementation can log false information in many cases. BE CAUTION that here we rely on inner implementation of http-proxy.
• Remove and simplify object-rest-spread is still in stage-3 related code. object-rest-spread should be stable now.
• Fix the github API unit test.
• Docs, etc

The modification should be backward compatible.

[codecov]

Codecov Report

Merging #74 (4b70398) into master (15d3f1c) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #74   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           62        67    +5     
  Branches        14        17    +3     
=========================================
+ Hits            62        67    +5     

Files	Coverage Δ
index.js	100.00% <100.00%> (ø)

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[vagusX]

This pr given us fine-grained control of proxy options function.

Would you like to fix this failing ci @xc1427

[vagusX]

• koa-proxies@0.12.4