Two modes to duplicate meshes along a curve. 

First one is the default one, which deform the mesh around curvy path. useful for lace or soft objects.

The second one is rigid duplicate, which does not deform the mesh. useful for hard object such as bike chains and tank treads

on the 3D view side panel, you can adjust the necessary property.

rotate mesh toward X axis as the along curve direction for better result.

update 1.2:

added more controls: including distance, offset, count, rotation, scale, stretch, squash and flip direction.

remove the "redo last". as in heavy scene, it lags and does not provide practical benefit. please use sliders in the side panel instead.

update 1.1 : 

removed unnecessary code related to renaming and pivot change.

soft cap all sliders, manually type a number to modify beyond the limit.