LANG-1059 Capitalize javadoc is incorrect

Add test to show that first character is upcased, not the first
(alphabetic) letter that is found

src/main/java/org/apache/commons/lang3/StringUtils.java

@@ -5749,6 +5749,7 @@ public class StringUtils {
      * StringUtils.capitalize("")    = ""
      * StringUtils.capitalize("cat") = "Cat"
      * StringUtils.capitalize("cAt") = "CAt"
+     * StringUtils.capitalize("'cat'") = "'cat'"
      * </pre>
      *
      * @param str the String to capitalize, may be null

src/test/java/org/apache/commons/lang3/StringUtilsTest.java

@@ -249,6 +249,13 @@ public class StringUtilsTest {
                 FOO_CAP, StringUtils.capitalize(FOO_CAP));
         assertEquals("capitalize(string) failed",
                 FOO_CAP, StringUtils.capitalize(FOO_UNCAP));
+
+        // Javadoc examples
+        assertNull(StringUtils.capitalize(null));
+        assertEquals("", StringUtils.capitalize(""));
+        assertEquals("Cat", StringUtils.capitalize("cat"));
+        assertEquals("CAt", StringUtils.capitalize("cAt"));
+        assertEquals("'cat'", StringUtils.capitalize("'cat'"));
     }
 
     @Test