Missing JAVA_HOME envvar leads to confusing message

[makkes]

The message "JAVA_HOME is not set. Jsdoc requires Java to run." is misleading since it implies that the missing JAVA_HOME envvar will cause JSDoc to fail which is not the case if the java executable is on the PATH (or similar for Windows).

I propose a change of the message that better reflects reality:

"JAVA_HOME is not set. Jsdoc may fail if it cannot find the java executable."

Better yet, grunt-jsdoc-plugin shouldn't check for a Java installation at all since the error message printed out by jsdoc itself is pretty self-explanatory:

>> node_modules/grunt-jsdoc/node_modules/jsdoc/jsdoc: 40: node_modules/grunt-jsdoc/node_modules/jsdoc/jsdoc: java: not found

This is related to #34.

[krampstudio]

Yes, totally agree. This is a mistake to check the JAVA_HOME and it caused a lot of confusion. I'll remove it.