Add custom projection

Author: sheindel

README.md

@@ -117,6 +117,15 @@ const zipData = shpwrite.zip(
 );
 ```
 
+## Custom .prj file
+To pass a custom [WKT string](http://www.opengeospatial.org/standards/wkt-crs) in the .prj file to define a different projection the prj option can be used:
+
+```js
+var options = {
+    prj: 'PROJCS["Amersfoort / RD New",GEOGCS["Amersfoort",DATUM["D_Amersfoort",SPHEROID["Bessel_1841",6377397.155,299.1528128]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Stereographic_North_Pole"],PARAMETER["standard_parallel_1",52.15616055555555],PARAMETER["central_meridian",5.38763888888889],PARAMETER["scale_factor",0.9999079],PARAMETER["false_easting",155000],PARAMETER["false_northing",463000],UNIT["Meter",1]]'
+}
+```
+
 ## API
 ### `write(data, geometrytype, geometries, callback)`
 

dist/index.d.ts

@@ -18,6 +18,7 @@ declare module "@mapbox/shp-write" {
   export interface DownloadOptions {
     folder?: string;
     filename?: string;
+    prj?: string;
     types?: {
       point?: string;
       polygon?: string;

indexTest.js

@@ -75,8 +75,8 @@ require('./src/download')({
     }
     ]
 }, {
-    file: 'shapefiles',
-    folder: 'shapefiles',
+    file: 'my_zip_filename',  // if empty, filename will be download.zip
+    folder: 'my_internal_shapes_folder', // leave empty to put in root
     outputType: 'blob',
     compression: 'DEFLATE',
     types: {

src/zip.js

@@ -1,7 +1,8 @@
-var write = require("./write"),
-  geojson = require("./geojson"),
-  prj = require("./prj"),
-  JSZip = require("jszip");
+var write = require("./write");
+var geojson = require("./geojson");
+var defaultPrj = require('./prj');
+var JSZip = require("jszip");
+
 
 module.exports = function (
   gj,
@@ -14,6 +15,8 @@ module.exports = function (
     zipTarget = zip.folder(options.folder);
   }
 
+  var prj = (options && options.prj) ? options.prj : defaultPrj;
+
   [
     geojson.point(gj),
     geojson.line(gj),