Set up artist bubble chart

Major changes:
- Set up preliminary artist bubble chart, font too small
- Wrote shell script for resetting database

spotifyvis/static/spotifyvis/scripts/artist_graph.js

@@ -0,0 +1,81 @@
+/**
+ * Draws the artist count graph as a bubble chart, and appends it the a designated parent element
+ * @param artistData: the artist counts data as an array of objects, of the format {'name': artist name, 'num_songs': 50}
+ * @param parentElem: the DOM element to append the artist graph to (as a string)
+ */
+function drawArtistGraph(artistData, parentElem) {
+    let margin = {top: 20, right: 30, bottom: 30, left: 40};
+    let width = 960 - margin.right - margin.left;
+    let height = 540 - margin.top - margin.bottom;
+
+    let color = d3.scaleOrdinal(d3.schemeCategory10);
+    let bubble = d3.pack(artistData)
+        .size([width, height])
+        .padding(1.5);
+
+    let svg = d3.select(parentElem)
+        .append("svg")
+        .attr("width", width + margin.right + margin.left)
+        .attr("height", height + margin.top + margin.bottom)
+        .attr("class", "bubble");
+
+    let nodes = d3.hierarchy(artistData)
+        .sum(function(d) { return d.num_songs; });
+
+    let node = svg.selectAll(".node")
+        .data(bubble(nodes).descendants())
+        .enter()
+        .filter(function(d) {
+            return !d.children;
+        })
+        .append("g")
+        .attr("class", "node")
+        .attr("transform", function(d) {
+            return "translate(" + d.x + "," + d.y + ")";
+        });
+
+    node.append("title")
+        .text(function(d) {
+            return `${d.name}: ${d.num_songs}`;
+        });
+
+    node.append("circle")
+        .attr("r", function(d) {
+            return d.r;
+        })
+        .style("fill", function(d,i) {
+            return color(i);
+        });
+
+    // artist name text
+     node.append("text")
+        .attr("dy", ".2em")
+        .style("text-anchor", "middle")
+        .text(function(d) {
+            return d.data.name.substring(0, d.r / 3);
+        })
+        .attr("font-family", "sans-serif")
+        .attr("font-size", function(d){
+            return d.r/5;
+        })
+        .attr("fill", "white");
+
+     // artist song count text
+     node.append("text")
+        .attr("dy", "1.3em")
+        .style("text-anchor", "middle")
+        .text(function(d) {
+            return d.data.num_songs;
+        })
+        .attr("font-family",  "Gill Sans", "Gill Sans MT")
+        .attr("font-size", function(d){
+            return d.r/5;
+        })
+        .attr("fill", "white");
+
+     d3.select(self.frameElement)
+         .style("height", height + "px");
+
+
+
+}