Don't autolink if authority is only "end" characters (#15)

This change stops these and other examples from being linked:

    http://.
    http://"
    http://<space>

Note that `http://` and `http://.` are valid URLs according to RFC 3986,
because `authority` can be zero or more `unreserved` characters. But we
don't autolink `http://` on its own or the trailing `.` of
`http://example.org.`

src/main/java/org/nibor/autolink/internal/Scanners.java

@@ -24,7 +24,7 @@ public static int findUrlEnd(CharSequence input, int beginIndex) {
         int curly = 0;
         boolean doubleQuote = false;
         boolean singleQuote = false;
-        int last = beginIndex;
+        int last = -1;
         loop:
         for (int i = beginIndex; i < input.length(); i++) {
             char c = input.charAt(i);

src/main/java/org/nibor/autolink/internal/UrlScanner.java

@@ -24,8 +24,11 @@ public LinkSpan scan(CharSequence input, int triggerIndex, int rewindIndex) {
         }
 
         int last = Scanners.findUrlEnd(input, afterSlashSlash);
+        if (last == -1) {
+            return null;
+        }
 
-        return new LinkSpanImpl(LinkType.URL, first, last + 1 );
+        return new LinkSpanImpl(LinkType.URL, first, last + 1);
     }
 
     // See "scheme" in RFC 3986

src/main/java/org/nibor/autolink/internal/WwwScanner.java

@@ -46,6 +46,9 @@ private static int findFirst(final CharSequence input, final int beginIndex, fin
 
     private static int findLast(final CharSequence input, final int beginIndex) {
         final int last = Scanners.findUrlEnd(input, beginIndex);
+        if (last == -1) {
+            return -1;
+        }
 
         // Make sure there is at least one dot after the first dot,
         // so www.something is not allowed, but www.something.co.uk is

src/test/java/org/nibor/autolink/AutolinkUrlTest.java

@@ -56,8 +56,14 @@ public void schemes() {
     }
 
     @Test
-    public void hostTooShort() {
+    public void authority() {
         assertLinked("ab://", "ab://");
+        assertLinked("http://", "http://");
+        assertLinked("http:// ", "http:// ");
+        assertLinked("\"http://\"", "\"http://\"");
+        assertLinked("\"http://...\", ", "\"http://...\", ");
+
+        assertLinked("http://a.", "|http://a|.");
     }
 
     @Test