Add params checking and refactor method signature for repos keys api, improve documentation.
Add params checking and refactor method signature for repos keys api, improve documentation.

GistBox/github,joshsoftware/github,durai145/github,davengeo/github,wicky-info/github,firstval/github,yaoxiaoyong/github,anabhilash619/github,cocktail-io/github,befairyliu/github,samphilipd/github,MalachiTatum/github,piotrmurach/github,peter-murach/github