Merge snap code into the Certbot repo

* merge .gitignore

* Move snapcraft.yml up one level.

* update source

* move test.sh to tox.ini

* use new tox.ini in .travis.yml

* move snap build code

* make script executable

* remove unused python3-dev

* don't use deprecated classic flag

* go back to stable channel

* add nginx in snap addons

* add deploy steps

* Add comments explaining external tox envs.

* error if not in CI

* don't use --depth

* remove old .travis.yml

* Add big comment about SNAP_TOKEN.

* Set all_branches: true.

* Add repo setting.

* run travis on tags

* Add more documenting comments to .travis.yml.

tox.ini

@@ -138,15 +138,22 @@ commands =
 
 [testenv:apacheconftest]
 commands =
-    {[base]pip_install} acme certbot certbot-apache certbot-compatibility-test
+    {[base]pip_install} acme certbot certbot-apache
     {toxinidir}/certbot-apache/tests/apache-conf-files/apache-conf-test --debian-modules
 passenv =
     SERVER
 
+[testenv:apacheconftest-external-with-pebble]
+# Run apacheconftest with pebble and Certbot outside of tox's virtual
+# environment.
+commands =
+    {[base]pip_install} certbot-ci
+    {toxinidir}/certbot-apache/tests/apache-conf-files/apache-conf-test-pebble.py --debian-modules
+
 [testenv:apacheconftest-with-pebble]
 commands =
-    {[base]pip_install} acme certbot certbot-apache certbot-ci certbot-compatibility-test
-    {toxinidir}/certbot-apache/tests/apache-conf-files/apache-conf-test-pebble.py --debian-modules
+    {[base]pip_install} acme certbot certbot-apache
+    {[testenv:apacheconftest-external-with-pebble]commands}
 
 [testenv:nginxroundtrip]
 commands =
@@ -250,6 +257,14 @@ commands =
         --cov-config=certbot-ci/certbot_integration_tests/.coveragerc
     coverage report --include 'certbot/*' --show-missing --fail-under=62
 
+[testenv:integration-external]
+# Run integration tests with Certbot outside of tox's virtual environment.
+commands =
+    {[base]pip_install} certbot-ci
+    pytest certbot-ci/certbot_integration_tests \
+        --acme-server={env:ACME_SERVER:pebble}
+passenv = DOCKER_*
+
 [testenv:integration-certbot-oldest]
 commands =
     {[base]pip_install} certbot