Merge pull request #4 from ZJONSSON/dev

First working copy
Oops, should be x not y
Pass the query object in .dates()
Remove rawDates from DF
Add Wiener (with Brownian Bridge) and Lognormal (Experimental)
Perform new if not an instance
Placeholder for Stream Object
Fix base.x
Return 0 for dcf is not own date
Fix dcf and add a bond object
Defaults in pyfy.interval
Switch calendar loop to top level
(i.e. continue looking until the resulting date is the same as the input date)
Add test for interval
Call calendars until they all result positive
(incrementing date by one on each fail)
Add a few calendars
Add tests for Iceland Calendar
New Random and Corr models for correlated structures
Move dates to query
Move inputs to an args object
Move rawDates processing to the query object