Allow applications to set crossorigin attribute

MR #68

Thanks to @stfsy

Set values of options to be optional

#67

Thanks to @timothy-bailey-redbox

Add referrerPolicy support

v1.2.1

bump to 1.2.1

Add nonce support

Thanks to @tanzhangwen
#57

fix timeout ReferenceError

Thanks the idea from @doxiaodong

Fix script error when script request error

v1.1.1

release 1.1.1

Handle error event

Handle <script> error event, thanks to @michaelvial

Use Original Url when Request Error

v1.0.2

release 1.0.2

Release 1.0.1

• Format code
• Update Readme

Release 1.0.0

• Remove Bower support
• Add jsonpCallback and jsonpCallbackFunction as options