Ignore .tmp files, don't ignore .txt

The forward_lomem.py crawler now generates .tmp files rather than .txt
files, so the latter can now be removed from .gitignore
foward_lomem.py redundant code removed

Removed all code pertaining to collection of followers (left over from
get_minimal_lomem.py). It now only collects followings - see comments
at head of file for explanation of why this is done.