fix: update tox workflow to use src/betamax path (#5)

The betamax directory was moved into the src directory but the tox
workflow was not updated to reflect this change. This commit updates
the tox workflow to use the new path.

Refs: betamaxpy#203, cf6aefe
Signed-off-by: Jaremy Hatler <hatler.jaremy@gmail.com>

tox.ini

@@ -13,19 +13,19 @@ commands = py.test {posargs}
 basepython = python2.7
 deps =
     flake8
-commands = flake8 {posargs} betamax
+commands = flake8 {posargs} src/betamax
 
 [testenv:py37-flake8]
 basepython = python3.7
 deps =
     flake8
-commands = flake8 {posargs} betamax
+commands = flake8 {posargs} src/betamax
 
 [testenv:docstrings]
 deps =
     flake8
     flake8-docstrings
-commands = flake8 {posargs} betamax
+commands = flake8 {posargs} src/betamax
 
 [testenv:release]
 deps =