source/install_source.rst: pip plugin depends on host pip

See merge request !791

The first badge will work fine right away while the second badge will
show "not found" until a release is made after merging this branch:
!718.

README.rst: Add status badges for PyPI release and Python versions

See merge request !719

Removed `resource.getrlimit()` functionality from app.py
Added `resource.getrlimit()` functionality to platform.py as function
Called new function from __init__.py of linux.py and unix.py

This needed to be implemented as Windows WSL
Does not currently support FUSE

Adding functionality to recognise Darwin as a platform in plaform.py

Previously safe_remove would attempt to unlink a path
Before attempting to remove it if it was a dir

Now it checks for a dir before that step