Revert package name change in bower.json

[wwuck]

The highcharts-export-csv name has already been registered in the bower package repository to point to https://github.com/wallynm/highcharts-export-csv, so this project will either need to claim control over that bower package registration or revert to the previous bower package name export-csv.

http://bower.io/search/?q=highcharts-export-csv