Add coverage command as Invoke task

.gitignore

@@ -7,3 +7,4 @@ test.log
 docs/
 !sites/docs
 _build
+.coverage

.travis.yml

@@ -10,7 +10,7 @@ install:
   - pip install -r dev-requirements.txt
 script:
   # Main tests, with coverage!
-  - coverage run --source=paramiko test.py --verbose
+  - invoke coverage
   # Ensure documentation & invoke pipeline run OK.
   # Run 'docs' first since its objects.inv is referred to by 'www'.
   # Also force warnings to be errors since most of them tend to be actual

tasks.py

@@ -26,5 +26,9 @@ www = Collection.from_module(_docs, name='www', config={
 def test(ctx):
     ctx.run("python test.py --verbose")
 
+@task
+def coverage(ctx):
+    ctx.run("coverage run --source=paramiko test.py --verbose")
 
-ns = Collection(test, docs=docs, www=www)
+
+ns = Collection(test, coverage, docs=docs, www=www)