docs for xmldict

[aguang]

Docs for XMLDict

Types of changes

This PR implements the following changes:
(Please tick any or all of the following that are applicable)

• ✨ New feature (A non-breaking change which adds functionality).
• 🐛 Bug fix (A non-breaking change, which fixes an issue).
• 💥 Breaking change (fix or feature that would cause existing functionality to change).

📋 Additional detail

• If you have implemented new features or behaviour
  • Provide a description of the addition in as many details as possible.
    Fix ERROR: type Response has no field data #31 which was about outdated documentation. It actually appears the docs had already been updated, but they had failed Travis and thus the docs did not get deployed. I could not reproduce the error on Travis. I also added lines for using BioServices with XMLDict.

☑️ Checklist

• 🎨 The changes implemented is consistent with the julia style guide.
• 📘 I have updated and added relevant docstrings, in a manner consistent with the documentation styleguide.
• 📘 I have added or updated relevant user and developer manuals/documentation in docs/src/.
• 🆗 There are unit tests that cover the code changes I have made.
• 🆗 The unit tests cover my code changes AND they pass.
• 📝 I have added an entry to the [UNRELEASED] section of the manually curated CHANGELOG.md file for this repository.
• 🆗 All changes should be compatible with the latest stable version of Julia.
• 💭 I have commented liberally for any complex pieces of internal code.

[kescobo]

@aguang Sorry this has languished for so long! Not sure exactly what the problem was, but once #36 is merged, it might be nice to revive this. Would you be open to that?

[kescobo]

@aguang I'm going to go ahead and merge this without worrying about the old test failures since it doesn't change any code.