Bump base nginx:alpine image (cachethq#318)

* Bump base image to 1.15.5-alpine

* Update .travis.yml

* output logs at cleanup

* correct service name

* Update test.full.bats

* Update test.full.bats

* use php artisan cachet:install

* new and improved!

* no debug

Bump base nginx:alpine image (cachethq#318)

* Bump base image to 1.15.5-alpine

* Update .travis.yml

* output logs at cleanup

* correct service name

* Update test.full.bats

* Update test.full.bats

* use php artisan cachet:install

* new and improved!

* no debug

Cachet Release v2.3.15

Cachet Release v2.3.14

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Cachet Release v2.3.12

Cachet Release v2.3.11

Cachet Release v2.3.10

Cachet Release v2.3.9

Cachet Release v2.3.8