Update LetsPlot sample notebook and screenshot in README

Fixes #307

Author: ileasile

docs/Screenshot.png

@@ -10,7 +10,7 @@
     {
      "data": {
       "text/html": [
-       "   <div id=\"VddKJb\"></div>\n",
+       "   <div id=\"ikKrcD\"></div>\n",
        "   <script type=\"text/javascript\" data-lets-plot-script=\"library\">\n",
        "       if(!window.letsPlotCallQueue) {\n",
        "           window.letsPlotCallQueue = [];\n",
@@ -21,7 +21,7 @@
        "       (function() {\n",
        "           var script = document.createElement(\"script\");\n",
        "           script.type = \"text/javascript\";\n",
-       "           script.src = \"https://cdnjs.cloudflare.com/ajax/libs/lets-plot/2.0.2/lets-plot.min.js\";\n",
+       "           script.src = \"https://cdn.jsdelivr.net/gh/JetBrains/lets-plot@v2.0.4/js-package/distr/lets-plot.min.js\";\n",
        "           script.onload = function() {\n",
        "               window.letsPlotCall = function(f) {f();};\n",
        "               window.letsPlotCallQueue.forEach(function(f) {f();});\n",
@@ -35,9 +35,9 @@
        "               var div = document.createElement(\"div\");\n",
        "               div.style.color = 'darkred';\n",
        "               div.textContent = 'Error loading Lets-Plot JS';\n",
-       "               document.getElementById(\"VddKJb\").appendChild(div);\n",
+       "               document.getElementById(\"ikKrcD\").appendChild(div);\n",
        "           };\n",
-       "           var e = document.getElementById(\"VddKJb\");\n",
+       "           var e = document.getElementById(\"ikKrcD\");\n",
        "           e.appendChild(script);\n",
        "       })();\n",
        "   </script>"
@@ -60,7 +60,7 @@
     "val data = mapOf<String, Any>(\n",
     "            \"cat1\" to listOf(\"a\", \"a\", \"b\", \"a\", \"a\", \"a\", \"a\", \"b\", \"b\", \"b\", \"b\"),\n",
     "            \"cat2\" to listOf(\"c\", \"c\", \"d\", \"d\", \"d\", \"c\", \"c\", \"d\", \"c\", \"c\", \"d\"))\n",
-    "val p = lets_plot(data)"
+    "val p = letsPlot(data)"
    ]
   },
   {
@@ -71,32 +71,32 @@
     {
      "data": {
       "text/html": [
-       "   <div id=\"N0aybL\"></div>\n",
+       "   <div id=\"OaSUgl\"></div>\n",
        "   <script type=\"text/javascript\" data-lets-plot-script=\"plot\">\n",
        "       (function() {\n",
        "           var plotSpec={\n",
-       "'mapping':{\n",
+       "\"mapping\":{\n",
        "},\n",
-       "'data':{\n",
+       "\"data\":{\n",
        "},\n",
-       "'kind':\"plot\",\n",
-       "'scales':[],\n",
-       "'layers':[{\n",
-       "'mapping':{\n",
-       "'x':\"cat1\",\n",
-       "'fill':\"cat2\"\n",
+       "\"kind\":\"plot\",\n",
+       "\"scales\":[],\n",
+       "\"layers\":[{\n",
+       "\"mapping\":{\n",
+       "\"x\":\"cat1\",\n",
+       "\"fill\":\"cat2\"\n",
        "},\n",
-       "'stat':\"count\",\n",
-       "'data':{\n",
-       "'cat2':[\"c\",\"c\",\"d\",\"d\"],\n",
-       "'cat1':[\"a\",\"b\",\"b\",\"a\"],\n",
-       "'..count..':[4.0,2.0,3.0,2.0]\n",
+       "\"stat\":\"count\",\n",
+       "\"data\":{\n",
+       "\"cat2\":[\"c\",\"c\",\"d\",\"d\"],\n",
+       "\"cat1\":[\"a\",\"b\",\"b\",\"a\"],\n",
+       "\"..count..\":[4.0,2.0,3.0,2.0]\n",
        "},\n",
-       "'position':\"stack\",\n",
-       "'geom':\"bar\"\n",
+       "\"position\":\"stack\",\n",
+       "\"geom\":\"bar\"\n",
        "}]\n",
        "};\n",
-       "           var plotContainer = document.getElementById(\"N0aybL\");\n",
+       "           var plotContainer = document.getElementById(\"OaSUgl\");\n",
        "           window.letsPlotCall(function() {{\n",
        "               LetsPlot.buildPlotFromProcessedSpecs(plotSpec, -1, -1, plotContainer);\n",
        "           }});\n",
@@ -110,7 +110,7 @@
     }
    ],
    "source": [
-    "val layer = geom_bar { \n",
+    "val layer = geomBar { \n",
     "    x = \"cat1\"\n",
     "    fill = \"cat2\"\n",
     "}\n",
@@ -139,7 +139,7 @@
    "name": "kotlin",
    "nbconvert_exporter": "",
    "pygments_lexer": "kotlin",
-   "version": "1.5.20-dev-4184"
+   "version": "1.6.0-dev-903"
   },
   "pycharm": {
    "stem_cell": {