results in terms of g

This pull-request modified the Climent et al. (1994) OpenQuake implementation, adjusting the computation of the ground motion in terms of (g). In the first implementation the ground motion are calculated in terms of (gals). 

Commit Summary

The computation [using Climent94] is made now in terms of (g) and not in terms of (gals) to be consistent with the OpenQuake standards.

File Changes 
M	openquake/hazardlib/gsim/climent_1994.py
M	openquake/hazardlib/tests/gsim/climent_1994_test.py
M	openquake/hazardlib/tests/gsim/data/CLI1994/CLI94_MEAN.csv

The test passed in my MAC:
Julio-Mac:gsim julio$ python check_gsim.py openquake.hazardlib.gsim.climent_1994.ClimentEtAl1994 data/CLI1994/CLI94_MEAN.csv
total of 1080 checks done, 1080 were successful and 0 failed.
0.1 seconds spent, avg rate is 9166.1 checks per seconds.
success rate = 100.0%
average discrepancy = 0.0002%
maximum discrepancy = 0.0124%
standard deviation = 0.0008%