Fix HTML errors in Javadoc.

Fix cases in the Javadoc comments where the characters need to be escaped
as HTML entities.

Author: ewanmellor

src/main/java/info/debatty/java/stringsimilarity/ShingleBased.java

@@ -39,7 +39,7 @@
  * strings or documents.
  *
  * Generally speaking, a k-gram is any sequence of k tokens. We use here the
- * definition from Leskovec, Rajaraman & Ullman (2014), "Mining of Massive
+ * definition from Leskovec, Rajaraman & Ullman (2014), "Mining of Massive
  * Datasets", Cambridge University Press: Multiple subsequent spaces are
  * replaced by a single space, and a k-gram is a sequence of k characters.
  *
@@ -65,7 +65,7 @@ public abstract class ShingleBased {
     /**
      *
      * @param k
-     * @throws IllegalArgumentException if k is <= 0
+     * @throws IllegalArgumentException if k is &lt;= 0
      */
     public ShingleBased(final int k) {
         if (k <= 0) {

src/main/java/info/debatty/java/stringsimilarity/interfaces/StringDistance.java

@@ -33,7 +33,7 @@ public interface StringDistance extends Serializable {
 
     /**
      * Compute and return a measure of distance.
-     * Must be >= 0.
+     * Must be >= 0.
      * @param s1
      * @param s2
      * @return