Fix some flake8 warnings in emsdk (#224)

Only some checks are enabled here in order to make this change
easier to review and less error prone.

Author: sbc100

.flake8

@@ -0,0 +1,3 @@
+[flake8]
+ignore = E111,E114,E501,E261,E266,E121,E402,E241,E701
+filename = emsdk

.travis.yml

@@ -6,7 +6,11 @@ services:
 before_install:
   - docker pull ubuntu:16.04
 
+install:
+  - pip install flake8==3.4.1
+
 script:
+  - flake8
   - set -o errexit
   - echo "running..."
   - docker build .