Include notebook demonstrating tree

Provides a quick demo showing how to use `tree` to get text-based and
HTML-based representations of a Zarr `Group` object.

notebooks/repr_tree.ipynb

@@ -0,0 +1,177 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import zarr"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "g1 = zarr.group()\n",
+    "g3 = g1.create_group('bar')\n",
+    "g3.create_group('baz')\n",
+    "g5 = g3.create_group('quux')\n",
+    "g5.create_dataset('baz', shape=100, chunks=10)\n",
+    "g7 = g3.create_group('zoo')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "/\n",
+      " +-- bar\n",
+      "     +-- baz\n",
+      "     +-- quux\n",
+      "     |   +-- baz[...]\n",
+      "     +-- zoo\n"
+     ]
+    }
+   ],
+   "source": [
+    "print(g1.tree())"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<style type=\"text/css\">\n",
+       "div.zarrTree {\n",
+       "    font-family: Courier, monospace;\n",
+       "    font-size: 11pt;\n",
+       "    font-style: normal;\n",
+       "}\n",
+       "\n",
+       "div.zarrTree ul,\n",
+       "div.zarrTree li,\n",
+       "div.zarrTree li > div {\n",
+       "    display: block;\n",
+       "    position: relative;\n",
+       "}\n",
+       "\n",
+       "div.zarrTree ul,\n",
+       "div.zarrTree li {\n",
+       "    list-style-type: none;\n",
+       "}\n",
+       "\n",
+       "div.zarrTree li {\n",
+       "    border-left: 2px solid #000;\n",
+       "    margin-left: 1em;\n",
+       "}\n",
+       "\n",
+       "div.zarrTree li > div {\n",
+       "    padding-left: 1.3em;\n",
+       "    padding-top: 0.225em;\n",
+       "    padding-bottom: 0.225em;\n",
+       "}\n",
+       "\n",
+       "div.zarrTree li > div::before {\n",
+       "    content: '';\n",
+       "    position: absolute;\n",
+       "    top: 0;\n",
+       "    left: -2px;\n",
+       "    bottom: 50%;\n",
+       "    width: 1.2em;\n",
+       "    border-left: 2px solid #000;\n",
+       "    border-bottom: 2px solid #000;\n",
+       "}\n",
+       "\n",
+       "div.zarrTree > ul > li:first-child > div {\n",
+       "    padding-left: 4%;\n",
+       "}\n",
+       "\n",
+       "div.zarrTree > ul > li:first-child > div::before {\n",
+       "    border: 0 none transparent;\n",
+       "}\n",
+       "\n",
+       "div.zarrTree ul > li:last-child {\n",
+       "    border-left: 2px solid transparent;\n",
+       "}\n",
+       "</style>\n",
+       "\n",
+       "<div class=\"zarrTree\">\n",
+       "<ul>\n",
+       "    <li><div>/</div>\n",
+       "        <ul>\n",
+       "            <li><div>bar</div>\n",
+       "                <ul>\n",
+       "                    <li><div>baz</div></li>\n",
+       "                    <li><div>quux</div>\n",
+       "                        <ul>\n",
+       "                            <li><div>baz[...]</div></li>\n",
+       "                        </ul>\n",
+       "                    </li>\n",
+       "                    <li><div>zoo</div></li>\n",
+       "                </ul>\n",
+       "            </li>\n",
+       "        </ul>\n",
+       "    </li>\n",
+       "</ul>\n",
+       "</div>\n"
+      ],
+      "text/plain": [
+       "/\n",
+       " +-- bar\n",
+       "     +-- baz\n",
+       "     +-- quux\n",
+       "     |   +-- baz[...]\n",
+       "     +-- zoo"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "g1.tree()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "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": "3.6.3"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}