Merge branch 'release-1.0'
Implement queue

- Implemented a queue ADT to help the design of breadth firsst traversal
of the binary tree.
- Introduced debugging facilities.
Use void* as item type in the queue

Operations on the content object are limited to assignment, that we can
easily do with pointers. This complicates a little the use of simple
types (we hace to have variables and pass their ponters when the data is
an int), but we have great flexibility (and the ability to actually use
the queue in the BST).
Make Valgrind smile

The dequeue operation involves the management of the returned element's
memory.
Fix Issue #4

Finally, BFS is in place :)
Merge branch 'issue4-print-rows' into next