repaired the wrong IP when using in localhost (Mac os x)

it returns “[“ when using beego in local host(Mac os x 10.9) , it
appears that Request.remoAddr returns “[::1]:****”
Merge pull request #399 from Max-Liu/master

repaired the wrong IP when using in localhost (Mac os x)
Merge pull request #400 from fuxiaohei/master

add api comments
remove contextBuffer fix #396
when panic show the request url