Add test case for coordinate conversion

[katiestahl]

Refer to below comment for original test. This test was removed since this request will no longer return 0 results after #336 is merged (nearest tx junction is always returned, no matter how far away)

After GenomicMedLab/cool-seq-tool#372 is addressed, we should add back in a test case similar to this that checks for an error if the requested coordinate conversion results in a coordinate that is over 100 base pairs away from the tx start/end

          Remove + add as new issue

Originally posted by @korikuzma in #336 (comment)