Fix travis-ci crash

It fixes the seg fault crash seen in travis builds.

Mostlikely the crash was caused by the exception below that appears if
the torch, cv2 and mathplotlib aren't imported in a right order.
```
ImportError: dlopen: cannot load any more object with static TLS
```
see #286 for more details.

fix typos in .travis.yml

tests/__init__.py

@@ -0,0 +1,7 @@
+import matplotlib
+matplotlib.use('agg')
+import cv2,torch
+
+# the above imports are fixing the TLS issue:
+# ```ImportError: dlopen: cannot load any more object with static TLS```
+# they were set after experimenting with the test sets on ubuntu 16.04