Use more obvious names for dates in let methods in report specs.

2013-02-20 is Wednesday so it is more 'human' to use it instead of
'today' (which is not true).
Fixed generating raport for a week.

It should generate a raport from Monday to Sunday (not from
last Sunday to Saturday).

[#1]
Merge pull request #2 from smt116/report-week-ignores-weekends

Report week ignores weekends