Shave ~1.5 seconds off 'names.json' load time

* Transform > 1 million from-disk seek/gets into from-ram seek/gets
Before
```
14:46:51.353 INFO : src/name.cpp:202: names load (disk->json.cpp)...
14:46:53.21 INFO : src/name.cpp:212: names load done.
14:46:55.553 INFO : src/name.cpp:202: names load (disk->json.cpp)...
14:46:57.333 INFO : src/name.cpp:212: names load done.
14:46:59.631 INFO : src/name.cpp:202: names load (disk->json.cpp)...
14:47:1.642 INFO : src/name.cpp:212: names load done.
```
After
```
14:48:52.115 INFO : src/name.cpp:190: names load (disk->ram->json.cpp)...
14:48:52.492 INFO : src/name.cpp:212: names load done.
14:48:54.884 INFO : src/name.cpp:190: names load (disk->ram->json.cpp)...
14:48:55.261 INFO : src/name.cpp:212: names load done.
14:48:57.741 INFO : src/name.cpp:190: names load (disk->ram->json.cpp)...
14:48:58.118 INFO : src/name.cpp:212: names load done.
```