Add tiles.hipsdescription module

[adl1995]

This commits adds a class named HipsDescription which provides methods for parsing the HiPS properties. It parses the given string and returns an object of OrderedDict. Additional getter methods are also included. For the test cases, a sample properties file was obtained from http://alasky.unistra.fr/DSS/DSSColor/properties

[coveralls]

Coverage decreased (-5.5%) to 94.545% when pulling ff3299abeb476ffb1937b6647f6bdae26d659e34 on adl1995:tiles.hipsdescription into b8e91aabfcd3347f17e044f64ba90522d4733826 on hipspy:master.

[coveralls]

Coverage decreased (-3.3%) to 96.721% when pulling dae30ac9cff524a0dc64bb638c5e6b62bc4011d4 on adl1995:tiles.hipsdescription into b8e91aabfcd3347f17e044f64ba90522d4733826 on hipspy:master.

[coveralls]

Coverage decreased (-3.3%) to 96.721% when pulling dae30ac9cff524a0dc64bb638c5e6b62bc4011d4 on adl1995:tiles.hipsdescription into b8e91aabfcd3347f17e044f64ba90522d4733826 on hipspy:master.

[cdeil]

@adl1995 - Can you please wrap up this pull request?

Once you've implemented comments, always leave a comment asking me to have another look, or if you don't know how to address one of my comments, leave a comment asking for clarification. If you just push new commits, I usually won't look at a PR until you ping me.

In this case: you're still not taking the OrderedDict as input in __init__, like I suggested in an inline comment above. Can you please change this? Is it clear what to do?

[adl1995]

@cdeil I just made another commit. Let me know if the __init__ method is being called in the correct manner now.

[coveralls]

Coverage decreased (-4.9%) to 95.082% when pulling a245521987a4971aaa70f842bb045f72512c760e on adl1995:tiles.hipsdescription into b8e91aabfcd3347f17e044f64ba90522d4733826 on hipspy:master.

[coveralls]

Coverage decreased (-4.9%) to 95.082% when pulling d369652b5edc9cda4705d0199a862bd8d226f526 on adl1995:tiles.hipsdescription into b8e91aabfcd3347f17e044f64ba90522d4733826 on hipspy:master.

[cdeil]

@adl1995 - I've just now pushed a commit to your branch for this PR: 3f9faed233a0d10cc771532d09f79eff7d279450

Some changes:

• Shorter name for the classmethods
• Fix return type annotation for classmethods
• Change version property to string (float is no good, because floats often can't be represented exactly on computers)
• Move example data file into a separate text file so that it's easier to read the test code file, and tha the HipsDesription.read method can be tested (and adding the common Astropy boilerplate of setup_package.py that makes sure the data file gets installed into site-packages with the package, and using an Astropy helper function to create the filename relative to the text module)
• Shorter docstrings
• Some other minor misc cleanup

I think this is ready to be merged, but I'll wait for travis-ci to run or comments until tomorrow.

[coveralls]

Coverage remained the same at 100.0% when pulling 3f9faed233a0d10cc771532d09f79eff7d279450 on adl1995:tiles.hipsdescription into b8e91aabfcd3347f17e044f64ba90522d4733826 on hipspy:master.

[cdeil]

@adl1995 - Thanks!