Improve output when problems with PATH

[shadowspawn]

Feature Request

Improve output when the installed version is not the active version.

Problem

The output from install gives a clue that there is a problem, but is very subtle, and looks like nvh is faulty. For example:

$ NVH_PREFIX=~/nvh nvh install 8

  installing : node/v8.14.0
       mkdir : /Users/john/nvh/nvh/versions/node/v8.14.0
       fetch : https://nodejs.org/dist/v8.14.0/node-v8.14.0-darwin-x64.tar.gz
   installed : v10.14.0

Proposed Solution

1. change the installed line to refer to version installed by nvh
2. if installed version not active version, add warning about active location. Suggest run nvh doctor?

Doctor

nvh doctor does already warn about some problems, but only if the user runs it.

$ NVH_PREFIX=~/nvh nvh doctor
...
Checking nvh install destination is in PATH...
possible problem, '/Users/john/nvh/bin' is not in PATH

[shadowspawn]

Work in progress:

$ NVH_PREFIX=~/oops nvh install 8

  installing : node/v8.14.0
       mkdir : /Users/john/oops/nvh/versions/node/v8.14.0
       fetch : https://nodejs.org/dist/v8.14.0/node-v8.14.0-darwin-x64.tar.gz
   installed : v8.14.0

Installed node to: /Users/john/oops/bin/node
but active node at: /usr/local/bin/node
(try running 'nvh doctor')

[shadowspawn]

Second try, present extra information in consistent format. Less noisy, so not annoying when it isn't an error condition (like preparing environment, running tests).

$ export NVH_PREFIX=~/DELETEME
$ nvh install lts

  installing : node/v10.14.1
       mkdir : /Users/john/DELETEME/nvh/versions/node/v10.14.1
       fetch : https://nodejs.org/dist/v10.14.1/node-v10.14.1-darwin-x64.tar.gz
   installed : v10.14.1 to /Users/john/DELETEME/bin/node
      active : v8.14.0 at /usr/local/bin/node

$ nvh install lts
   installed : v10.14.1 to /Users/john/DELETEME/bin/node
      active : v8.14.0 at /usr/local/bin/node
$ export PATH=${NVH_PREFIX}/bin:$PATH
$ nvh install lts
   installed : v10.14.1

[shadowspawn]

Resolved in v6.1.0