Merge pull request #111 from BluntBlade/master

更新接口代码
[ci skip]
七牛海外服务器上传
Update README.md
ok
允许海外服务器高速上传
Update README.md
string keys to symbol
ok
usage added
real merge
Merge pull request #112 from dekexu/master

七牛up_host的修改
将 mime-types 依赖版本升级到 2.4.3 。