Move homePath() and netrcFilename to platform files.

Gets them properly defined at build time instead of switching on
runtime.GOOS at runtime.
Easier to change install location.
s/iif/if/
don't need to append 'X' suffix to dyno sizes anymore
styleguide update
Fixes for Heroku dev clouds.

Read creds from proper netrc entry and disable SSL verification if
HEROKU_API_URL is set.

Fixes #80.
suggest help topics as help commands

fixes #78