Reduce precision of output JSON files to 4 decimals
Only set JSON precision after first writing the grid
Revert "Only set JSON precision after first writing the grid"

This reverts commit 487d4dea42eba311b6d2b935df495999bb4d7bbd.
Update JSON data with lower precision (4 decimal place)
Merge pull request #2 from enthought/enh/json-precision

Reduce precision of output JSON