add 'alias' command for querying and setting the alias (#126)

* add 'alias' command for querying and setting the alias

* calculate coverage only on library files, e.g., ignoring cli and test files

* remove py34 and add py37

* readd py33, remove it from travis as it seems to be a travis limitation only

* use xenial dist for travis, regular does not support py37..

tox.ini

@@ -1,13 +1,13 @@
 [tox]
-envlist=py33,py34,py35,py36,flake8
+envlist=py33,py34,py35,py36,py37,flake8
 skip_missing_interpreters = True
 
 [tox:travis]
-2.7 = py27
-3.3 = py34
+3.3 = py33
 3.4 = py34
 3.5 = py35
 3.6 = py36
+3.7 = py37
 
 [testenv]
 passenv = TRAVIS TRAVIS_JOB_ID TRAVIS_BRANCH
@@ -17,7 +17,7 @@ deps=
   voluptuous
   typing
 commands=
-    py.test --cov pyHS100
+    py.test --cov --cov-config=tox.ini pyHS100
 
 [testenv:flake8]
 deps=flake8
@@ -29,3 +29,10 @@ commands=mypy --silent-imports pyHS100
 
 [flake8]
 exclude = .git,.tox,__pycache__,pyHS100/tests/fakes.py
+
+[coverage:run]
+source = pyHS100
+branch = True
+omit =
+  pyHS100/cli.py
+  pyHS100/tests/*