Add Japan map

I generated map data for Japan.
Original map data is in the public domain. It is published at following site.
http://www.naturalearthdata.com/downloads/10m-cultural-vectors/10m-admin-1-states-provinces/

I chose <a href="http://en.wikipedia.org/wiki/List_of_FIPS_region_codes_(J%E2%80%93L)#JA:_Japan">FIPS 10-4</a> as region code and removed `JA` prefix.
This works well with [fluent-plugin-geoip](https://github.com/y-ken/fluent-plugin-geoip).

![](http://gyazo.com/46ea9c6455770598ca6d4c30e3cd31c0.png)

### convert script

Used [jVectormap converter](https://github.com/bjornd/jvectormap/tree/0.2.3)

```sh
#!/bin/sh

output=map.japan.js

python converter.py \
  --width 900 \
  --country_name_index 8 \
  --country_code_index 57 \
  --longitude0 135 \
  --where "iso_a2 = 'JP'" \
  --projection aea \
  --name japan \
  --minimal_area 100000000 \
  --language en \
  --insets '[{"codes": ["JA47"], "width": 200, "left": 100, "top": 100}]' \
  --input_file_encoding utf-8 \
  ne_10m_admin_1_states_provinces/ne_10m_admin_1_states_provinces.shp \
  $output

sed -i -e 's/JA//g' $output
sed -i -e 's/japan_aea_en/japan/' $output
```