Add input year to output data file names

[trynthink]

Revise input data file names to include _YYYY, e.g., mseg_res_com_cdiv_2015.json, so that it is clear from what year of AEO data those files were derived.

As part of this change, add a component to the Travis build that will cause it to fail if the YYYY values in mseg_res_com_cz_YYYY.json, cpl_res_com_cz_YYYY.json, and metadata_YYYY.json do not all match.

[trynthink]

Make sure that the mseg and cpl JSON files in /web (added in commit 625d452033940fcb3fcfc0a69ba6840cccdee9dc) also have _YYYY in their file names.

Don't forget to uncomment _YYYY support htcl_totals.py, run.py, and ecm_prep.py (based on modifications in 75cfac8e217f37819b14f0a816fe4a3e37128e20).

Update mseg_meta.py to revise metadata.json to also include _YYYY in its name. Update the input data preparation scripts to look for a metadata.json file with _YYYY in the file name and verify that the year matches correctly.

Update the .gitignore as needed to block files from being committed in the wrong locations. (This applies to both the files in /web and /supporting_data.)