adding fdsn example

FDSN-data-download.ipynb

@@ -0,0 +1,68 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "This examples shows how to download restricted waveform data from the geofon database."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from pyrocko.fdsn import ws\n",
+    "from pyrocko import util, io, trace\n",
+    "\n",
+    "\n",
+    "# select time range\n",
+    "tmin = util.stt('2015-09-16 22:54:33')\n",
+    "tmax = util.stt('2015-09-17 00:54:33')\n",
+    "\n",
+    "# select networkID, StationID, Location, Channel\n",
+    "# asterisk '*' as wildcard is possible\n",
+    "selection = [('X9', '*', '*', 'HHZ', tmin, tmax)] \n",
+    "# Example above: Select restricted network X9, all stations, all locations,\n",
+    "# vertikal component only, 80Hz\n",
+    "\n",
+    "# Read access-token for the restricted network from file \n",
+    "token=open('token.asc', 'rb').read()   # 'rb' required for unicode to byte conversion\n",
+    "\n",
+    "# setup a waveform data request\n",
+    "request_waveform = ws.dataselect(site='geofon',selection=selection,token=token)\n",
+    "\n",
+    "# Instead of the token, username and password can be given explicitely via:\n",
+    "# request_waveform = ws.dataselect(site='geofon',selection=selection,user=user,passwd=passwd)\n",
+    "# where 'user' and 'passwd' are to be entered as strings.\n",
+    "\n",
+    "\n",
+    "# write the incoming data stream to 'traces.mseed'\n",
+    "with open('traces.mseed', 'wb') as file:         # 'wb' - same reason as 'rb' above\n",
+    "    file.write(request_waveform.read())"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.5.2"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}