`install.sh` installation location

[lann]

Currently this installs to whatever directory I happen to be in, which is a little surprising.

I'm actually not sure what the best alternative is here. Heroku's equivalent install.sh requires sudo and installs to /usr/local/bin, bailing out if that dir isn't in PATH.

[lann]

@mikkelhegn

[mikkelhegn]

I feel that myself :-)

I think we should do the following:

1. Default to / suggest to use /usr/local/bin, as this will solve putting it in PATH, and the user will have to go figure that out. Like the Heroku script.
2. Give an option to use the current dir. I've found that useful if I quickly need to try something with canary or a specific version, but overwriting my default Spin in usr/local/bin

If going down the packet manager route, I think they all have their own prescribed way of doing this - e.g., Homebrew and the opt/ directory.

[mikkelhegn]

#641