setup.py: add docopt as a dependency
download.py: use docopt for command-line options

Docopt provides slightly nicer help messages for silly fools like myself
who try running ``ruaumoko-download -h`` and discover a huge file names
``-h`` on their machine :).
download: add some informative logging of progress

In verbose mode, log location of download and download progress.
setup.py: add six as a dependency

six is a compatibility library which smooths the differences between
Python 2 and 3.
download: allow customisation of download location

Allow configuration of download location and file paths from command
line. (This will allow for easier testing later on.)
add Py2 compatibility shim for TemporaryDirectory

Python 2 dows not have TemporaryDirectory in the tempfile module. Add in
a small back-ported compatibility shim[1] for Python 2.

[1] http://stackoverflow.com/questions/19296146/with-tempfile-temporarydirectory
setup.py: enable ruaumoko-download for all Pythons

With 42c984b, ruaumoko-download now works on Python 2 as well.
download: allow selection of chunks

Allow for specification of which chunks to download.
remove reliance on six

The amount of six which we were using was rather small. Move urlunsplit
into _compat. It turns out that iteritems was in fact *never* used :(.
download: hard-code zip and TIFF file paths

Having the expected zip and TIFF file paths customisable from the
command-line may have been a case of premature-configurability.
download: hard-code DEM path on server

Since the DEM zip filenames are hard-coded, it now makes little sense to
configure the path.
requirements: add docopt to sync with setup.py
_compat: backport TemporaryDirectory implementation

This is the implementation currently in 3.4 backported to 2.7's weakref
implementation. Add appropriate attribution and source to copyright
banner.

Tehe 3.4 implementation has the strong advantage of being a *lot*
smaller than the original Stack Overflow implementation :).
gitignore: add *.egg-info directories

Add the .egg-info directories which setuptools likes to sprinkle around
the source tree.
AUTHORS: add @rjw57

Adding myself to AUTHORS as suggested in #12.
Merge pull request #13 from rjw57/add-egg-info-to-gitignore

gitignore: add *.egg-info directories
Merge pull request #14 from rjw57/add-rjw57-to-authors

AUTHORS: add @rjw57
Merge pull request #12 from rjw57/download-tool-rework

Download tool rework
remove duplication in requirements.txt and setup.py

The requirements.txt file and setup.py's ``install_requires`` do serve
different purposes. I only recently got more of a handle on what those
purposes are. See [1] for a good overview.

A nice feature of pip discussed in [1] and which I was not aware of is
the ability to use a ``-e .`` idiom to add **ourselves** to the
requirements and thereby include the requirements listed in setup.py
while preserving the ability for requirements.txt to specify precise
library versions if required.

Using this idiom nicely reduces the duplication of dependency
information between requirements.txt and setup.py but retains the
ability to, for example, have Cython listed explicitly in
requirements.txt but only being an implicit dependency in setup.py.

The de-duplication also reduces the testing burden; we need only test
the ``pip install -r requirements.txt`` installation rather than testing
both requirements.txt and setup.py to catch missing any missing
dependencies.

[1] https://caremad.io/blog/setup-vs-requirement/
add a simple stub travis configuration

This does nothing more than attempt to install the requirements.