validate input table
read data_table ULs
use data tabels in test_functionfit

use data file in test_plotting

add test data
adapt examples
use pytest.raises in exception tests
use sed_conversion in guess to do proper integrated flux

Conflicts:
	examples/CrabNebula_proton.py
	gammafit/core.py
	gammafit/plot.py
	gammafit/utils.py
fix conflicts
table units only work on astropy development (>=0.4)
Merge pull request #36 from zblz/table-data

Use astropy.table.Table as input data