Merge pull request qiniu#67 from hustKiwi/master

Merge pull request qiniu#62 from SunLn/master

up.qiniu.com -> upload.qiniu.com

Merge pull request qiniu#51 from qiniu/fix_file_resume_chunk_upload_bug

check file size when resume upload

Merge pull request qiniu#32 from qiniupd/11087_fix_offset_bug_when_re…

…upload

11087 fix offset bug when reupload

Merge pull request qiniu#26 from qiniupd/8165_continue_uploading_when…

…_web_failed

add resume upload feature

Merge pull request qiniu#14 from qiniupd/8351_add_x_val_feature

8351 add x val feature again

update pre code