Bug fix about import fault from command line

[suzuki-shm]

Hello @christophertbrown

In the current implementation, I couldn't call iRep from command line.

$ git clone git@github.com:christophertbrown/iRep.git
$ cd iRep
$ pip install .
$ irep

Traceback (most recent call last):
  File "/Users/suzukishinya/.pyenv/versions/3.6.2_irep/bin/irep", line 18, in <module>
    import iRep.iRep as iRep
  File "/Users/suzukishinya/.pyenv/versions/3.6.2/envs/3.6.2_irep/lib/python3.6/site-packages/iRep/iRep.py", line 34, in <module>
    from mapped import get_reads as mapped
ModuleNotFoundError: No module named 'mapped'

I have fixed this simple import error.

[christophertbrown]

Thanks!