Upgrade to spotbugs 3.1.2

Changelog:

https://github.com/spotbugs/spotbugs/blob/release-3.1/CHANGELOG.md#312---2018-02-24

pom.xml

@@ -245,7 +245,7 @@
       <plugin>
         <groupId>com.github.spotbugs</groupId>
         <artifactId>spotbugs-maven-plugin</artifactId>
-        <version>3.1.1</version>
+        <version>3.1.2</version>
         <configuration>
           <effort>Max</effort>
           <omitVisitors>CrossSiteScripting,DefaultEncodingDetector,FindNullDeref</omitVisitors>
@@ -353,10 +353,10 @@
       <version>2.9.4</version>
     </dependency>
     <dependency>
-        <groupId>com.github.spotbugs</groupId>
-        <artifactId>spotbugs-annotations</artifactId>
-        <version>3.1.1</version>
-        <scope>provided</scope>
+      <groupId>com.github.spotbugs</groupId>
+      <artifactId>spotbugs-annotations</artifactId>
+      <version>3.1.2</version>
+      <scope>provided</scope>
     </dependency>
     <dependency>
       <groupId>com.google.code.findbugs</groupId>