Configure the linked binary location

[rob0rt]

Creating a ~/bin folder in the user's home directory is a bit imposing, especially without a . prefix so it's not hidden on most OSes; supporting an alternative install path for the linked binary other than ~/bin/bit (for example, co-locating it in ~/.bvm) would be appreciated/ reasonable.

I'd personally like to suggest just putting it in ~/.bvm/bit (since the folder is already there) and updating the documentation accordingly. $PATH has to be updated already for the current install directory scheme, so this change doesn't seem to be particularly disruptive.

[GiladShoham]

This is a left overs since the days we haven't implemented the path update automatically.
so we put it there to reduce the friction of adding a step to manually update the path.
now that we already implemented it, we can replace the bin location.