Merge branch 'gitlab-ci' into develop

We now use gitlab-ci, mostly due to unresolvable OOM errors in Circle CI

* gitlab-ci:
  README: Fix typo
  README: use gitlab CI badge
  Delete circle.yml.
  Add gitlab-ci.yml

.gitlab-ci.yml

@@ -0,0 +1,28 @@
+image: circleci/android:api-27-alpha
+
+before_script:
+  - export GRADLE_USER_HOME="$(pwd)/.gradle"
+  - export GRADLE_OPTS='-Dorg.gradle.daemon=false'
+
+cache:
+  paths:
+    - .gradle
+
+stages:
+  - build
+
+build:
+  stage: build
+  script:
+    - ./gradlew assembleCiDebug
+    - ./gradlew testCiDebugUnitTest
+    - ./gradlew jacocoTestReportCiDebug
+    - awk -F"," '{ instructions += $4 + $5; covered += $5 } END { print covered, "/", instructions, "instructions covered"; print 100*covered/instructions, "% covered" }' Calendula/build/reports/jacoco/ciDebug/jacoco.csv
+    - if grep -r '* Created by' Calendula/src/; then exit 1; fi
+  artifacts:
+    paths:
+      - Calendula/build/outputs/
+      - Calendula/build/reports/tests/
+      - Calendula/build/test-results/
+      - Calendula/build/reports/jacoco/
+    expire_in: 1 week

README.md

@@ -1,5 +1,5 @@
 ![](https://tec.citius.usc.es/calendula/github-assets/calendula_promo_google_play.png)
-# Calendula [![CircleCI](https://circleci.com/gh/citiususc/calendula/tree/develop.svg?style=shield)](https://circleci.com/gh/citiususc/calendula/tree/develop)
+# Calendula [![Gitlab CI](https://gitlab.com/calendula-ci/calendula/badges/develop/build.svg)](https://gitlab.com/calendula-ci/calendula/pipelines)
 
 Calendula is an Android assistant for personal medication management, aimed at those who have trouble following their medication regimen, forget to take their drugs, or have complex schedules that are difficult to remember.