Added note that the Go language is required for installation (for users that don't use Homebrew)
Merge pull request #91 from AlphaHydrae/go-install-instructions

Readme note that the Go language is required for installation
Renames DIRENV_PATH to direnv in the stdlib. It's not exported.
Add direnv_apply_dump function to stdlib

It works with the new `direnv apply-dump` command to
convert a dumped environment (typically from a different process)
into a series of `export` statements which are then evaluated
in the current process.

Fixes #85
direnv_apply_dump: run the dump command given in <argv>, rather than taking a file containing dump output
direnv_apply_dump: use $direnv
rename direnv_apply_dump -> direnv_load