Igorpro

Added entry for the Igor Pro language. Here are some examples of use already on github:
https://github.com/bgallarda/IgorPro
https://github.com/dleifohcs/srs-igor
https://github.com/willsALMANJ/Igor-ProW
https://github.com/david-hoffman/Igor-Data-Analysis
https://github.com/yamad/igorutils
https://github.com/nanophotonics/procedures

I have no idea what I'm doing so I am submitting this on the faint hope that Travis will enlighten me :smiley: