Add maven install code to build wiki page

[arundasan91]

Hello,

Please see this as a suggestion. I have been running into this and only this error while installing CaffeOnSpark, always. So it would be nice to test it out locally and update if necessary.

Always, I have to do sudo apt-get install maven before I build using sudo make build inside CaffeOnSpark directory.

Please add this line to the wiki : https://github.com/yahoo/CaffeOnSpark/wiki/build

It would mitigate errors that numerous CaffeOnSpark users face while building it.

Thanks, Arun