Update HITRAN module to use class-based query API

[migueldvb]

This modifies the HITRAN module to follow the common class based API specification. It does not
support yet any output format description apart from the the 160-byte fixed-width format used in HITRAN 2004. I think that support for user-defined formats could be added in a different PR.

fixes #824

[astropy-bot]

Hi there @migueldvb 👋 - thanks for the pull request! I'm just a friendly 🤖 that checks for issues related to the changelog and making sure that this pull request is milestoned and labeled correctly. This is mainly intended for the maintainers, so if you are not a maintainer you can ignore this, and a maintainer will let you know if any action is required on your part 😃.

I noticed the following issue with this pull request:

• Changelog entry not present (or pull request number missing) and neither the Affects-dev nor the no-changelog-entry-needed label are set

Would it be possible to fix this? Thanks!

If there are any issues with this message, please report them here.

[migueldvb]

I forgot to add the Changelog file to the PR. I think everything should be there now.

[keflavich]

Awesome, looks good. I gave it a once-over and approve, but I should read more carefully before giving official approval.

[codecov]

Codecov Report

Merging #1028 into master will increase coverage by 0.18%.
The diff coverage is 80.95%.

@@            Coverage Diff             @@
##           master    #1028      +/-   ##
==========================================
+ Coverage   63.97%   64.16%   +0.18%     
==========================================
  Files         143      144       +1     
  Lines       11348    11362      +14     
==========================================
+ Hits         7260     7290      +30     
+ Misses       4088     4072      -16

Impacted Files	Coverage Δ
astroquery/hitran/__init__.py	100% <100%> (ø)	⬆️
astroquery/hitran/utils.py	57.5% <57.5%> (ø)
astroquery/hitran/core.py	94.54% <94.54%> (ø)

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[keflavich]

It looks like there's one legit failure, hitran seems not to be indexed:
https://travis-ci.org/astropy/astroquery/jobs/337249515#L2012

This issue: https://travis-ci.org/astropy/astroquery/jobs/337249517 is probably not real, but some sort of travis configuration issue.

[migueldvb]

oh yes, I'll fix the linking of hitran in the docs and see if this solves the failure.

EDIT: the docs build problem is gone.

[bsipocz]

@migueldvb - There is a minor conflict, would you mind to rebase?

[migueldvb]

I rebased this branch. Hopefully all the CI checks will pass after the rebase!

[keflavich]

@migueldvb Could you rebase this once more? @bsipocz just finished fixing our tests, so we will finally be able to safely merge this. It looks ready to merge to me.

[migueldvb]

Sorry that I missed fixing this for 0.3.8. This is now rebased on master.