Update .envrc

Handle sourcing the file using the absolute file path.
Add bash/{foldr,map}

Handy utilities from http://www.cyber.com.au/~twb/.bin/{foldr,map}.
Add misc/{tmux2xclip,xclip2tmux}

Script helpers to bridge the X clipboard and the tmux paste buffers.
Update misc/{tmux2xclip,xclip2tmux}

Add options parsing for passing options to xclip/tmux.
Update bash/functions/path

Style fixes: lowercase local variables, arithmetic tests (( )), ...
Update bash/functions/bashmod

Style fixes: lower-case local variables, arithmetic expressions (( )).