add test
fixed index out of range.

How to reproduce this issue:

* create unwanted series (for example: columns and fields count mismatched. put 2 fields, put 1 column)
* insert data with modified client library.

then, InfluxDB will panic with following message

```
panic: runtime error: index out of range

goroutine 20 [running]:
runtime.panic(0x8a9040, 0x104d997)
        /usr/local/go/src/pkg/runtime/panic.c:266 +0xb6
datastore.(*LevelDbShard).Write(0xc2100b0480, 0xc211182a80, 0xa,
0xc210405408, 0x1, ...)
        /home/chobie/src/influxdb/src/datastore/leveldb_shard.go:89
+0x98f
datastore.(*LevelDbShardDatastore).Write(0xc210077d80, 0xc21843eb00,
0x0, 0x0)
        /home/chobie/src/influxdb/src/datastore/leveldb_shard_datastore.go:163
+0xf2
cluster.(*WriteBuffer).write(0xc2100d5150, 0xc21843eb00)
        /home/chobie/src/influxdb/src/cluster/write_buffer.go:88 +0x86
cluster.(*WriteBuffer).handleWrites(0xc2100d5150)
        /home/chobie/src/influxdb/src/cluster/write_buffer.go:79 +0xb7
created by cluster.NewWriteBuffer
        /home/chobie/src/influxdb/src/cluster/write_buffer.go:43 +0x24f
```