fix up 701
Merge pull request #26 from why404/release/v3.2.2

fix up 701
[bug_fixed] lib/qiniu/tokens/qbox_token.rb => method generate_token => undefined method signature
Merge pull request #27 from zhouguangming/bug_fixed

感谢修正！不过由于历史遗留原因 lib/qiniu/tokens/qbox_token.rb 尚保留在sdk代码里边但并未实际使用。请求签名认证程序使用的是  
Qiniu::RS::Utils.generate_qbox_signature(url,params) , 所以不影响sdk正常使用。
MissingArgsError should get a key_list
Merge pull request #28 from zhouguangming/bug_fixed

MissingArgsError should get a key_list // very nice!
refactor UP.upload_with_token
Merge pull request #29 from zhouguangming/bug_fixed

refactor UP.upload_with_token
disabled wm
add Qiniu::RS.generate_download_token()
docs updated
fix encoding comments
rewrite docs
updated Gemfile.lock
Merge pull request #31 from why404/feature/download_token

Feature/download token