some minor refinement

1. Change the corner widget color;
2. Change the markdown.css's style to not let it wrap a line.

src/resources/icons/corner_menu_cur.svg

@@ -3,7 +3,7 @@
 <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
 <svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
 	 width="512px" height="512px" viewBox="0 0 512 512" enable-background="new 0 0 512 512" xml:space="preserve">
-<path style="fill:#15AE67" d="M296,136c0-22.002-17.998-40-40-40s-40,17.998-40,40s17.998,40,40,40S296,158.002,296,136z M296,376
+<path style="fill:#9C27B0" d="M296,136c0-22.002-17.998-40-40-40s-40,17.998-40,40s17.998,40,40,40S296,158.002,296,136z M296,376
 	c0-22.002-17.998-40-40-40s-40,17.998-40,40s17.998,40,40,40S296,398.002,296,376z M296,256c0-22.002-17.998-40-40-40
 	s-40,17.998-40,40s17.998,40,40,40S296,278.002,296,256z"/>
 </svg>

src/resources/icons/corner_tablist_cur.svg

@@ -5,7 +5,7 @@
 	 width="512px" height="512px" viewBox="0 0 512 512" enable-background="new 0 0 512 512" xml:space="preserve">
 <g id="Icon_3_">
 	<g>
-		<path style="fill:#15AE67" d="M64,384h384v-42.666H64V384z M64,277.334h384v-42.667H64V277.334z M64,128v42.665h384V128H64z"/>
+		<path style="fill:#9C27B0" d="M64,384h384v-42.666H64V384z M64,277.334h384v-42.667H64V277.334z M64,128v42.665h384V128H64z"/>
 	</g>
 </g>
 </svg>

src/resources/markdown.css

@@ -60,7 +60,6 @@ p, ul, ol {
 }
 pre {
     padding: 0px 24px;
-    white-space: pre-wrap;
     background-color: #f8f8f8;
     border-radius: 3px;
     border: 1px solid #cccccc;
@@ -77,7 +76,6 @@ pre code {
    padding: 0;
    border: none;
    background: transparent;
-   white-space: pre-wrap;
    overflow: auto;
    color: #444444;
 }