added sun/pos.py, equivalent of Solarsoft IDL sunpos.py
added sun/pos.py, equivalent of Solarsoft IDL sunpos.py

dpshelio/sunpy,mjm159/sunpy,Alex-Ian-Hamilton/sunpy,dpshelio/sunpy,Alex-Ian-Hamilton/sunpy,mjm159/sunpy,dpshelio/sunpy,Alex-Ian-Hamilton/sunpy