Error in obfuscation of lat/long

[atruskie]

Reported by Dez:

Latitude – Longitude appears to be randomising before obfuscating. This is producing a misplacement of the Lat-Long greater than the code originally was set for of 10m. The error appears to be up to 100km

• Double check the unit tests - we're meant to be rounding to nearest ±20m
• Possibly: store the jittered location so it does not move around
  • may not need to once it jitters correctly (the moving effect would be small)
• Possibly: remove jitter for users with write permissions

Confirmed by @AntMt

[cofiem]

Updated unit tests to actually test for rounding (based on ~10m accuracy at 0.0001 degrees).
Jitter is not stored, only calculated, and still applies for users with write permissions.

[cofiem]

Lat/longs for site do not seem to be obfuscated since Rails4 migration.

[cofiem]

Fixed in cf1a88b