[MS Edge bug] Response header string starts with \n

[davidgarry]

Trim headerStr to fix a MS Edge bug with xhr.getAllResponseHeaders method which send a string starting with a "\n" character

Sources :

• https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/5403401/
• https://connect.microsoft.com/IE/feedbackdetail/view/1929694/ie-edge-incorrectly-return-the-header-with-a-leading-new-line-character
• Microsoft IE/Edge doesn't seem to be pulling down client configuration settings. exceptionless/Exceptionless.JavaScript#23

[davemevans]

The build fails due to JSCS errors. Please run grunt lint and fix the reported style errors.

[davidgarry]

Yes, I will do it !