Add method to removeCurrentDate.
Rename setCurrentDate into moveTo, removeCurrentDate into comeBack
Merge pull request #13 from rezzza/issue_4

Add method to removeCurrentDate.
Supports of date and gmdate functions.
Merge pull request #14 from rezzza/issue_5

Supports of date and gmdate functions.
Update readme.
Add notion of timezone for many tests.
Add support of gettimeofday(). Fixed #2.