move computation of start/end in constructor + set them as property to save computation time
	modified:   libnessus/objects/host.py
            correct constructor (attribute not assigned with self)
            add __repr__
            add get_hostprop_attr
            add get_summary_total_cves
            add get_report_items
            add get_total_vuln
	modified:   libnessus/test/test_host.py
            add new tests
	modified:   libnessus/test/test_nessus.py
            add samples for the tests
Merge pull request #2 from bmx0r/master

NessusHost additional methods (@bmx0r)