fix(datepicker): fix days shown with brasil DST change

Depending on the browser timezone, the datepicker might show duplicate days when the DST causes hours to go forward - this will happen in São Paulo, Brazil timezone in 18th October 2014, so the datepicker will show two 18th days and miss the 19th, as shown in #1133. This particular error doesn't occur in GMT/CET timezones.

I added a basic test just to check if the datepicker is showing consecutive days, so when there is a duplicate day, the test fails.

Problem is that to test it, we need to change the browser timezone, so I created a Gulp task called test:timezone:BR that changes the timezone to São Paulo before running the tests. To see the tests fail, you need to run ```gulp test:timezone:BR```
I guess there might be an easier way to incorporate this on the default test task?

I then added Pedro's fix commit, but now the some other tests fail when running with the Brasil timezone. Not sure why.