Fix Java tests

[zugaldia]

We've got a few failing tests that weren't being run:

:lib:test

com.mapbox.services.geojson.FeatureCollectionTest > fromJson FAILED
    com.google.gson.JsonParseException at FeatureCollectionTest.java:14
        Caused by: java.lang.ClassNotFoundException at FeatureCollectionTest.java:14

com.mapbox.services.geojson.FeatureCollectionTest > toJson FAILED
    com.google.gson.JsonParseException at FeatureCollectionTest.java:27
        Caused by: java.lang.ClassNotFoundException at FeatureCollectionTest.java:27

com.mapbox.services.geojson.FeatureTest > fromJson FAILED
    com.google.gson.JsonParseException at FeatureTest.java:14
        Caused by: java.lang.ClassNotFoundException at FeatureTest.java:14

com.mapbox.services.geojson.FeatureTest > toJson FAILED
    com.google.gson.JsonParseException at FeatureTest.java:22
        Caused by: java.lang.ClassNotFoundException at FeatureTest.java:22

com.mapbox.services.geojson.GeometryCollectionTest > fromJson FAILED
    com.google.gson.JsonParseException at GeometryCollectionTest.java:14
        Caused by: java.lang.ClassNotFoundException at GeometryCollectionTest.java:14

com.mapbox.services.geojson.GeometryCollectionTest > toJson FAILED
    com.google.gson.JsonParseException at GeometryCollectionTest.java:22
        Caused by: java.lang.ClassNotFoundException at GeometryCollectionTest.java:22

60 tests completed, 6 failed