Unmatched hosts should generate human-readable error messages

[gibson042]

The current behavior is a bit opaque.

$ eshost -h fake -se true
(node:9811) UnhandledPromiseRejectionWarning: TypeError: Cannot set property 'name' of undefined
    at /usr/lib/node_modules/eshost-cli/bin/eshost.js:385:17
    at Array.map (<anonymous>)
    at runInEachHost (/usr/lib/node_modules/eshost-cli/bin/eshost.js:383:11)
    at Object.<anonymous> (/usr/lib/node_modules/eshost-cli/bin/eshost.js:318:5)
    at Module._compile (internal/modules/cjs/loader.js:1147:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1167:10)
    at Module.load (internal/modules/cjs/loader.js:996:32)
    at Function.Module._load (internal/modules/cjs/loader.js:896:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)
    at internal/main/run_main_module.js:17:47
(node:9811) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:9811) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.