So I've taken your suggestions, but I haven't made any progress yet.
Here's the latest error.
Binary sketch size: 1,076 bytes (of a 32,256 byte maximum)
/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/avrdude -C/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf -v -v -v -v -patmega328p -carduino -P/dev/tty.usbmodem431 -b115200 -D -Uflash:w:/var/folders/7l/l7qms65j7lqgq95x9k6ndd9w0000gn/T/build2288264899857103370.tmp/basic_blink.cpp.hex:i
avrdude: Version 5.11, compiled on Sep 2 2011 at 18:52:52
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2009 Joerg Wunsch
System wide configuration file is "/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf"
User configuration file is "/Users/neal/.avrduderc"
User configuration file does not exist or is not a regular file, skipping
Using Port : /dev/tty.usbmodem431
Using Programmer : arduino
Overriding Baud Rate : 115200
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding
avrdude done. Thank you.