~/.bpmrc and no more Korean in environment

.bpmrc can be used to declare important paths, e.g., Homebrew
install loation, etc.

In fact, the last commit made `bpm load` no longer idempotent, and made
the PATH variable oscillate in some cases.  This is because most other
bashrc files were always prepending paths, so bash_insert_path_if_not
made things very sensitive to how many times you do `bpm load`.  So,
it's wise to let environment to always do bash_insert_path PATH, and
keep some important PATH configs in .bpmrc instead.