Add 'today' parameter to .parse method

[novikserg]

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Refs #295 This one allows Chronic.parse method to receive today: true param alongside a string to parse to allow parsing ambiguous week days by name. For example:

Time.now                             #=> Sun Aug 27 23:18:25 PDT 2006
Chronic.parse('sunday')              #=> Sun Sep 03 12:00:00 PDT 2006
Chronic.parse('sunday', today: true) #=> Sun Aug 27 12:00:00 PDT 2006

Somewhat a quick workaround for now since new version is going to change it all anyway.

[davispuh]

yeah I think this can be used, what do you @leejarvis think? also might as well merge beta branch in master and release it as there are some fixes and it's been sitting there for ages.