Mention that Oracle JDK 6 library will fail to build

So people won't encounter and ask the same question as I did just now ;)

Author: Raymond Liu <raymond.liu@intel.com>

Closes #49 from colorant/doc and squashes the following commits:

90bf2aa [Raymond Liu] Mention that Oracle JDK 6 library will fail to build
Minor changes in Java POJO WordCount example
add gh_link jekyll plugin to docs
Finished Flink-928

Taskmanagers are now displayed in the web interface @rmetzger

Author: Jonathan <Jonathan@Hasenburg.de>

Closes #43 from JonathanH5/webclient and squashes the following commits:

5cc5f72 [Jonathan] Finished Flink-928 and simplified how new pages to the WebInterface are added
[FLINK-932] Introduce automatic generation of semantic props for projections

This closes #29
Fix various error messages and invalid JavaDocs.
[FLINK-996] Fix for bug in union replacement

This closes #56