[webcontent] heads-up to upgrade httpclient to 4.5

Hi,

It's been a long while. I just want to do heads-up: I'd like to
upgrade the httpclient dependency from 4.4 to the latest of 4.5 with
this ticket:
- https://issues.apache.org/jira/browse/APA-73

After that, I also would like to cut a release of v2.1. At the moment,
we have two fixes for v2.1:
- https://issues.apache.org/jira/projects/APA/versions/12334392

Please let me know if you want other fixes this time or have any other
concerns or remarks.

Thanks,

Woonsan