按月份列分区 ，每个自然月一个分片，格式 between操作解析的范例。
<tableRule name="sharding-by-month">
<rule>
<columns>create_time</columns>
<algorithm>sharding-by-month</algorithm>
</rule>
</tableRule>
<function name="sharding-by-month" class="org.opencloudb.route.function.PartitionByMonth">
<property name="dateFormat">yyyy-MM-dd</property>
<property name="sBeginDate">2014-01-01</property>
</function>
配置说明：
columns： 分片字段，字符串类型
dateFormat ： 日期字符串格式
sBeginDate ： 开始日期
PartitionByMonth partition = new PartitionByMonth();
partition.setDateFormat("yyyy-MM-dd");
partition.setsBeginDate("2014-01-01");
partition.init();
Assert.assertEquals(true, 0 == partition.calculate("2014-01-01"));
Assert.assertEquals(true, 0 == partition.calculate("2014-01-10"));
Assert.assertEquals(true, 0 == partition.calculate("2014-01-31"));
Assert.assertEquals(true, 1 == partition.calculate("2014-02-01"));
Assert.assertEquals(true, 1 == partition.calculate("2014-02-28"));
Assert.assertEquals(true, 2 == partition.calculate("2014-03-1"));
Assert.assertEquals(true, 11 == partition.calculate("2014-12-31"));
Assert.assertEquals(true, 12 == partition.calculate("2015-01-31"));
Assert.assertEquals(true, 23 == partition.calculate("2015-12-31"));
