Big integers as metric values invoke no HTTP response from BF.

It turns out Jackson handles BigIntegers just fine (test case added). Problem is BF expects a numeric metric value to be either Integer, Long or Double. We don't deal with BigInteger. (Eventually we should).

Until we start handling BigInteger, let's start sending a BAD REQUEST to the clients so they know the submit failed. This should be documented somewhere in API documentation. 

Stack trace:

java.lang.RuntimeException: Unknown metric value typeclass java.math.BigInteger
	at com.rackspacecloud.blueflood.types.DataType.getMetricType(DataType.java:45)
	at com.rackspacecloud.blueflood.types.Metric.<init>(Metric.java:34)
	at com.rackspacecloud.blueflood.inputs.formats.JSONMetricsContainer.toMetrics(JSONMetricsContainer.java:63)
	at com.rackspacecloud.blueflood.inputs.formats.JSONMetricsContainerTest.testBigIntHandling(JSONMetricsContainerTest.java:82)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:601)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:77)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:195)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:63)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:601)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)