Add makefile targets for doc8 lint, fix formatting/spelling issues

Change-Id: I0f45ffe0ba94fab89f9b38c9b73ed7b9091f1795
diff --git a/docs/source/bbr.rst b/docs/source/bbr.rst
index 88856bd..dfdaa39 100644
--- a/docs/source/bbr.rst
+++ b/docs/source/bbr.rst
@@ -7,7 +7,7 @@
 is responsible to emulate ONOS and VOLTHA in order to quickly reply to
 any message that BBSim sends.
 
-Here is a graph of the measuraments of BBSim performance captured over
+Here is a graph of the measurements of BBSim performance captured over
 10 runs with different PON Layout
 
 .. figure:: ./_static/bbr_runs.png
@@ -47,7 +47,7 @@
    $ ./bbr -onu 16 -pon 4
 
 ``bbr`` will run to completion and output the time it took to bring all
-the ONUs to the ``dhcp_ack`` state. If the ``bbr`` process doesn’t exit,
+the ONUs to the ``dhcp_ack`` state. If the ``bbr`` process doesn't exit,
 it means something went wrong.
 
 Debugging and issue reporting