closes #20 memory leak issue

Resolved:
```
sh build_all.sh && valgrind ./bin/time_tracker.cpp.bin
==19879== Memcheck, a memory error detector
==19879== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==19879== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==19879== Command: ./bin/time_tracker.cpp.bin
==19879==
[INFO] [26/01/2013 11:40:47.187] Result is 3
==19879==
==19879== HEAP SUMMARY:
==19879==     in use at exit: 0 bytes in 0 blocks
==19879==   total heap usage: 109 allocs, 109 frees, 44,853 bytes allocated
==19879==
==19879== All heap blocks were freed -- no leaks are possible
==19879==
==19879== For counts of detected and suppressed errors, rerun with: -v
==19879== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2)
```