Print message when setting PWM fails.

This prevents the car from completely stopping if there is a weak connection
between the host and the peripheral motor board. Otherwise, a single failed
set_pwm call will halt the host.

updated dockerfile

Fix source code of parts directory, to follow PEP8 rules

Fixed conda install path

Update install_software.md

Update install_software.md

The conda install path was pointing to `envs/mac.yml`, but nowhere before that instruction does it tell the reader to `cd` into the `install` subdirectory first, so for the command to work, `install` must be prepended to the path.

remove non-core parts

other parts were moved here: https://github.com/autorope/donkey_parts_library

support offline networks

proofread readme

Deploy to pypi only once when using build matrix

Makes use of TravisCI build stages. Note that this feature is still
in beta.

Master

Dev 2.5.0

Added screwless  camera design to documentation