Add to readme that java is required to work

[gotsalyuk]

Greetings, why don’t you indicate in readme that you need to install java for the selenium test, Instead of 'If you use BrowserMob Proxy in a Java application or Selenium test'. What is obvious to you is not clear to many. I visited several forums where people describe a problem with running working code, what they are answered with corrections that does not solve the problem