adding --open-mode {r|w} option to filter files opened for read or write

Updating version to v0.12

Removing debug traces (sorry)

Reseting optind before parsing PROGRESS_ARGS (related to issue Xfenne…

…c#69 and probably Xfennec#68)

Adding support for PROGRESS_ARGS environement variable. Version updat…

…ed to 0.10.

Updating version to 0.9

Updating version to 0.8

Updating version to 0.7.

Small update about Mac OSX support.

Updated documentation about -p option. Version is now 0.6.