Fix amber watcher

[faustinoaq]

Description of the Change

Currently amber watcher stops if an error is found during development, it should stop only if an error is found at begining

A side effect is that an amber background process is never killed so the project keep running silently showing unexpected outputs when you run amber watch again.

Good (stopping server if there is any error at beginning of development)

➜  forum amber w                             
10:47:48 Watcher    | Watching 36 files (server reload)...
10:47:48 Watcher    | Building project Forum...
Error in src/forum.cr:1: while requiring "../config/*"

require "../config/*"
^

Syntax error in config/routes.cr:45: for empty hashes use '{} of KeyType => ValueType'

{}
^

10:47:49 Watcher    | Compile time errors detected. Shutting down..

Bad (stopping if an error is found during development, server should keep running, waiting for a possible fix)

10:46:00 Watcher    | File changed: ./config/routes.cr
10:46:00 Watcher    | Watching 1 files (server reload)...
10:46:00 Watcher    | Building project Forum...
10:46:08 Watcher    | Terminating app Forum...
10:46:08 Watcher    | Starting Forum...
10:46:08 Server     | (INFO) [Amber 0.6.3] serving application "Forum" at http://0.0.0.0:3000
10:46:08 Server     | (INFO) Server started in development.
10:46:08 Server     | (INFO) Startup Time 00:00:00.000369000
10:46:08 Watcher    | Watching 7 files (browser reload)...
10:46:11 Request    | Started 2018-01-14 10:46:11 -05:00
10:46:11 Request    | Status: 200  Method: GET  Pipeline: web Format: html
10:46:11 Request    | Requested Url: /
10:46:11 Request    | Time Elapsed: 641.0µs
10:46:11 Headers    | Host: ["0.0.0.0:3000"]
10:46:11 Headers    | Connection: ["keep-alive"]
10:46:11 Headers    | Cache-Control: ["max-age=0"]
10:46:11 Headers    | Upgrade-Insecure-Requests: ["1"]
10:46:11 Headers    | User-Agent: ["Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"]
10:46:11 Headers    | Accept: ["text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8"]
10:46:11 Headers    | DNT: ["1"]
10:46:11 Headers    | Referer: ["http://0.0.0.0:3000/"]
10:46:11 Headers    | Accept-Encoding: ["gzip, deflate"]
10:46:11 Headers    | Accept-Language: ["es,en-US;q=0.9,en;q=0.8,es-419;q=0.7"]
10:46:11 Headers    | Cookie: ["amber.session=eyJfZmxhc2giOiJ7fSIsImNzcmYudG9rZW4iOiIwZnJWbWxXMElfWDdsYkhXTXFtRXhjeTIxcHpuV3V6azdva3NLNXNlTU80In0%3D--Mc%2Bv6uNizy%2Bd2WkMYdNyZexr4f0%3D"]
10:46:11 Cookies    | amber.session: #<HTTP::Cookie:0x564dd94bad20>
10:46:11 Session    | _flash: {}
10:46:11 Session    | csrf.token: 0frVmlW0I_X7lbHWMqmExcy21pznWuzk7oksK5seMO4
10:46:16 Watcher    | File changed: ./config/routes.cr
10:46:16 Watcher    | Watching 1 files (server reload)...
10:46:16 Watcher    | Building project Forum...
Error in src/forum.cr:1: while requiring "../config/*"

require "../config/*"
^

Syntax error in config/routes.cr:45: for empty hashes use '{} of KeyType => ValueType'

{}
^

10:46:17 Watcher    | Unknown error occurred, Shutting down...

Alternate Designs

No

Benefits

We avoid the need of executing amber watch again and again after every code error. Also we can kill amber server properly avoiding unexpected background processes.

Possible Drawbacks

No

[elorest]

Seems to be the same as this issue.
#475

[elorest]

Good fix.