Adding initial contents for "Binary Tree | Set 1 (Introduction)".
Moving java/binarytreeintro to java/binarytree.

Each subsection will now have their own directory.
Adding .gitignore to g4g/java directory.

This will ignore .classpath and .project files, and g4g/bin directory
to begin with.
Fixed whitespace and access modifier in binarytreeintro/Node.java.
Reorganizing source packaging structure (adding Java packages).
Merge branch 'master' of https://github.com/srikanthsrs/g4g