* Don't bother reading empty version files
* Implement version file read in pure bash
Is faster with usual sized version files, slower with degenerate cases.
We're going to eliminate the need to mandatorily use `pyenv init --path`.
We can't delete it yet for backward compatibility.
Besides, there's one other use case for it: to enable shims but without
shell integration, e.g. for noninteractive shells.
To be a full-fledged replacement for `pyenv init -` however,
it needs to do rehashing.
Now the setup is to add to both rc and profile:
1) set PYENV_ROOT
(can do it unconditionally -- since if you change it,
you need to update all places anyway since any of them can be run first)
2) Add `pyenv` to PATH if not already there
3) eval "$(pyenv init -)"
Not a breaking change, old setup will continue to work.
...rather than login mode.
I couldn't get rid of the warning that `pyenv init -` no longer sets path until I did this. It looks like setting only on the login shell wasn't enough to hide the warning in other shells I opened. This fits with [how rbenv does the same thing](https://github.com/rbenv/rbenv/blob/master/libexec/rbenv-init#L74).
I'm way out of my depth here, so someone who knows about shell types should definitely review this.
* Update install instructions for Bash and Zsh
* Synchronize README.md with `pyenv init`
* Add a ~/.bash_profile note
* Concatenate shims activation into installation for brevity
(Pyenv can't be used meaningfully without shims anyway)
Otherwise, we'd need to duplicate all the ~/.profile shenanigans in both sections
* Update based on feedback
* Proofread
E.g. for a GUI session, ~/.profile is executed by the GUI login "shell" at its startup
so one needs to fully log out and log back in.
Before that, the change would only be seen by shells explicitly started as login shells.
