Update the Logo url

On NPM the logo was broken because the url was relative.

README.md

@@ -1,5 +1,5 @@
 <a href="https://github.com/styled-components/styled-components">
-  <img alt="styled-components" src="./docs/assets/logo.png" height="150px" />
+  <img alt="styled-components" src="https://raw.githubusercontent.com/styled-components/brand/master/styled-components.png" height="150px" />
 </a>
 <br />
 

docs/assets/logo.svg

@@ -1,36 +0,0 @@
-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<svg width="318px" height="318px" viewBox="0 0 318 318" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
-    <!-- Generator: Sketch 40.1 (33804) - http://www.bohemiancoding.com/sketch -->
-    <title>logo</title>
-    <desc>Created with Sketch.</desc>
-    <defs>
-        <rect id="path-1" x="0" y="0" width="318" height="318"></rect>
-        <mask id="mask-2" maskContentUnits="userSpaceOnUse" maskUnits="objectBoundingBox" x="0" y="0" width="318" height="318" fill="white">
-            <use xlink:href="#path-1"></use>
-        </mask>
-    </defs>
-    <g id="Page-1" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
-        <g id="logo">
-            <g id="Group-2">
-                <use id="Rectangle" stroke="#000000" mask="url(#mask-2)" stroke-width="8" xlink:href="#path-1"></use>
-                <text id="styled" font-family="FiraCode-Regular, Fira Code" font-size="36" font-weight="normal" letter-spacing="0.179999992" fill="#000000">
-                    <tspan x="35.16" y="234">styled</tspan>
-                </text>
-                <text id="components" font-family="FiraCode-Regular, Fira Code" font-size="36" font-weight="normal" letter-spacing="0.179999992" fill="#000000">
-                    <tspan x="34.1" y="280">components</tspan>
-                </text>
-                <g id="Group" transform="translate(23.000000, 19.000000)" fill="#000000" font-weight="normal">
-                    <text id="&lt;" font-family="FiraCode-Regular, Fira Code" font-size="140" letter-spacing="0.699999928">
-                        <tspan x="0" y="132">&lt;</tspan>
-                    </text>
-                    <text id="&gt;" font-family="FiraCode-Regular, Fira Code" font-size="140" letter-spacing="0.699999928">
-                        <tspan x="186" y="131">&gt;</tspan>
-                    </text>
-                    <text id="💅" font-family="AppleColorEmoji, Apple Color Emoji" font-size="100" letter-spacing="0.49999997">
-                        <tspan x="85" y="125">💅</tspan>
-                    </text>
-                </g>
-            </g>
-        </g>
-    </g>
-</svg>