Switch to using scikit image as primary IO lib

Now, we prefer scikit image as the image IO library, as it is
pip install-able and doesn't reverse the colours.

Also some formatting changes throughout, none of which afffect acutal
code.

Changes to be committed:
      modified:   timestream/__init__.py
      modified:   timestream/manipulate/__init__.py
      modified:   timestream/parse/__init__.py
Install freeimage dev package in travis CI
Rewrite read_image and add tests
Replace all X.imread calls with read_image

read_image (from timestream.parse) is a wrapper around scikit image's
imread using freeimage. This change allows us to use a single image
reading function to avoid weird bugs where we have several image reading
functions at once. This also allows us to change our mind as to which
image IO library to use and only need to change one function.

Changes to be committed:
      modified:   timestream/__init__.py
      modified:   timestream/manipulate/pipecomponents.py
      modified:   timestream/parse/__init__.py
Tidy the travis CI config
Pin pillow at an extant version

Pillow was pinned at 1.1.7, a version no longer in PyPI.
Output JPG files by default

* timestream/__init__.py (create): Change the default image format to JPG.
Address strange characters in the csv file.

* util/derandui.py (_addCsv): We make sure we ignore characters that are not
encodable.
Selected columns will now be shown in derandomization.

* timestream/manipulate/pipecomponents.py (DerandomizeTimeStreams.derandStruct):
We added a text to accompany the pot id. This text is to be put on top of the
pot image.
(DerandomizeTimeStreams.createCompoundImage): Add text from derandStruct to each
pot. We use a font slightly smaller than the subsection title.
* util/derandui.py (_createDerandStruct): For each item in master list that is
selected, we add selection to the pot string.