v0.7.1

Update version to 0.7.1 in package.json

package.json

 {
   "name": "geomag-algorithms",
-  "version": "0.7.0",
+  "version": "0.7.1",
   "homepage": "http://geomag.usgs.gov/",
   "repository": "https://github.com/usgs/geomag-algorithms.git",
   "description": "Geomagnetism algorithms.",