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]
Replaced gem list with gemspec in Gemfile.
Added Guard for easier developing.

It is much easier if tests are run after changes without running
`rspec` command.
Merge pull request #3 from smt116/gemspec-in-gemfile

Gemspec in gemfile
Merge pull request #2 from smt116/report-week-ignores-weekends

Report week ignores weekends
Removed whitespace
Fixed issue #5 with timert raising an error for the last day of the year.
Added tmp to the .gitignore
Enabled reports for the past weeks
Enabled reports for the past months