[base64-dark theme] Background selected color

Changed background selected color to #303030, previous #202020 value is too dark.
https://github.com/cristatus/brackets-darker/issues/12

Author: herkulano

theme/base16-dark.css

@@ -9,7 +9,7 @@
 */
 
 .cm-s-base16-dark.CodeMirror {background: #151515; color: #e0e0e0;}
-.cm-s-base16-dark div.CodeMirror-selected {background: #202020 !important;}
+.cm-s-base16-dark div.CodeMirror-selected {background: #303030 !important;}
 .cm-s-base16-dark .CodeMirror-gutters {background: #151515; border-right: 0px;}
 .cm-s-base16-dark .CodeMirror-guttermarker { color: #ac4142; }
 .cm-s-base16-dark .CodeMirror-guttermarker-subtle { color: #505050; }