Add drop_cookie helper

[Patil2099]

Fixes #144

[thangngoc89]

I’m not sure if this PR is read my for review or not but this is definitely not adding drop_cookie but rather modifing set_cookie ‘s signature

[aantron]

I’m not sure if this PR is read my for review or not but this is definitely not adding drop_cookie but rather modifing set_cookie ‘s signature

Indeed, thanks @thangngoc89.

@Patil2099 Rather than modifying set_cookie, we need to add a new function drop_cookie that calls set_cookie internally in its implementation.

[aantron]

Closing in favor of #169.