Move Economy logic out of main plugin class and into MoneyThing.

This means that MoneyThingParser now needs to pass along an Economy instance instead of a MobArena instance, which makes the dependency a little more focused and reasonable.

Also adds MoneyThingParser tests.

src/test/java/com/garbagemule/MobArena/things/MoneyThingParserTest.java

@@ -0,0 +1,55 @@
+package com.garbagemule.MobArena.things;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.CoreMatchers.not;
+import static org.hamcrest.CoreMatchers.nullValue;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.mockito.Mockito.mock;
+
+import net.milkbowl.vault.economy.Economy;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+public class MoneyThingParserTest {
+
+    private MoneyThingParser subject;
+
+    @Rule
+    public ExpectedException exception = ExpectedException.none();
+
+    @Before
+    public void setup() {
+        Economy economy = mock(Economy.class);
+        subject = new MoneyThingParser(economy);
+    }
+
+    @Test
+    public void noPrefixNoBenjamins() {
+        MoneyThing result = subject.parse("500");
+
+        assertThat(result, is(nullValue()));
+    }
+
+    @Test
+    public void shortPrefix() {
+        MoneyThing result = subject.parse("$500");
+
+        assertThat(result, not(nullValue()));
+    }
+
+    @Test
+    public void longPrefix() {
+        MoneyThing result = subject.parse("money:500");
+
+        assertThat(result, not(nullValue()));
+    }
+
+    @Test
+    public void numberFormatForNaughtyValues() {
+        exception.expect(NumberFormatException.class);
+        subject.parse("$cash");
+    }
+
+}