Guards Should Use Environment

Previously all of the guard behavior was triggered by the contents of
environment variables.  In a Spring Boot application, looking at the
environment isn't the only way to get configuration.  This change updates the
guards to use the Environment for configuration retrieval.

[resolves #30]

Signed-off-by: Ben Hale <bhale@vmware.com>

pom.xml

@@ -26,7 +26,6 @@
     <properties>
         <java.version>1.8</java.version>
         <jsr305.version>3.0.2</jsr305.version>
-        <junit-pioneer.version>0.6.0</junit-pioneer.version>
         <spring-boot.version>2.2.7.RELEASE</spring-boot.version>
 
         <!-- Plugins -->
@@ -65,12 +64,6 @@
             <scope>provided</scope>
         </dependency>
 
-        <dependency>
-            <groupId>org.junit-pioneer</groupId>
-            <artifactId>junit-pioneer</artifactId>
-            <version>${junit-pioneer.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>org.mariadb.jdbc</groupId>
             <artifactId>mariadb-java-client</artifactId>