Remove the obsolete tutorial (fixes #69)
Batch rename hdist -> hit

This was done by the command:

sed -i -e 's/\<hdist\>/hit/g' `git grep -l "\<hdist\>"`

Further patches will polish the rest of the things by hand.
Finish the renaming hdist -> hit

We also need to rename the files
Rename hdistconfig and hashdistconfig to hitconfig
Rename hdist_id -> hit_id
Rename hdist_path -> hit_path
Rename hdist_un/pack -> hit_un/pack
Rename _extract_hdist_pack -> _extract_hit_pack
Rename core.hdist_recipe -> core.hit_recipe