download.sh: Trap interrupt; Add sudo prompt info; Remove wget requirement
download.sh: Trap interrupt; Add sudo prompt info; Remove wget requirement

 Add interrupt handler so entire script exits if user hits ctrl-c on sub-command
 Add info before prompting for password using sudo
 Remove wget requirement since OSX does not have wget in default system
 Add `-C -` to curl package download to continue or skip existing packages

PaulHigin/PowerShell,KarolKaczmarek/PowerShell,jsoref/PowerShell,TravisEz13/PowerShell,bingbing8/PowerShell,daxian-dbw/PowerShell,bmanikm/PowerShell,jsoref/PowerShell,daxian-dbw/PowerShell,bmanikm/PowerShell,PaulHigin/PowerShell,KarolKaczmarek/PowerShell,JamesWTruher/PowerShell-1,JamesWTruher/PowerShell-1,JamesWTruher/PowerShell-1,PaulHigin/PowerShell,bmanikm/PowerShell,daxian-dbw/PowerShell,TravisEz13/PowerShell,bmanikm/PowerShell,bingbing8/PowerShell,TravisEz13/PowerShell,jsoref/PowerShell,jsoref/PowerShell,KarolKaczmarek/PowerShell,bingbing8/PowerShell,JamesWTruher/PowerShell-1,KarolKaczmarek/PowerShell,bmanikm/PowerShell,TravisEz13/PowerShell,jsoref/PowerShell,bingbing8/PowerShell,PaulHigin/PowerShell,daxian-dbw/PowerShell,KarolKaczmarek/PowerShell,bingbing8/PowerShell