Avoid ls warning when there are no .txt files at all in the /tmp dir. (#254)
Correctly avoiding double fetch of the same experiment from S3. (#254)

Don't forget, each fetch from S3 costs $$$ :)
Tracking X, Y, Z position for a measurement at the top level. (#254)

The main reason is simplicity - X, Y, Z and time are really important
keys and it doesn't really make sense to embed them under a sub-key.
/CC @cosmin
Displaying correctly session measurements which no longer have X, Y, Z embedded under the subject_position key. (#254)
Merge pull request #262 from ami-lab/b/#254-location-based-trajectory-merging

B/#254 location based trajectory merging