Make .equals(null) not throw NPE (#84)

* build.xml: use source and target 1.8

The codebase uses method references, which requires source 1.8. Target
must be at least as high as source.

* Allow .equals(null) to work

Three classes have .equals methods which throw exceptions for
.equals(null). Fix them.

build.xml

@@ -25,8 +25,8 @@
     <mkdir dir="${build}/classes/" />
     <javac srcdir="${source}"
            destdir="${build}/classes/"
-           target="1.5"
-           source="1.5"
+           target="1.8"
+           source="1.8"
            debug="on" debuglevel="lines,vars,source"
            includeantruntime="false"
            fork="true" />

src/main/java/com/dd/plist/NSData.java

@@ -124,6 +124,7 @@ public String getBase64EncodedData() {
 
     @Override
     public boolean equals(Object obj) {
+        if (obj == null) return false;
         return obj.getClass().equals(this.getClass()) && Arrays.equals(((NSData) obj).bytes, this.bytes);
     }
 

src/main/java/com/dd/plist/NSDate.java

@@ -147,6 +147,7 @@ public Date getDate() {
 
     @Override
     public boolean equals(Object obj) {
+        if (obj == null) return false;
         return obj.getClass().equals(this.getClass()) && this.date.equals(((NSDate) obj).getDate());
     }
 

src/main/java/com/dd/plist/NSDictionary.java

@@ -303,6 +303,7 @@ public int count() {
 
     @Override
     public boolean equals(Object obj) {
+        if (obj == null) return false;
         return obj.getClass().equals(this.getClass()) && ((NSDictionary) obj).dict.equals(this.dict);
     }