Implements additional unit tests for integral_flux_image in spectral_cube
Fixes mistake in angle units definitin in image utils.py and affected npred_general tutorial script
Merge with master
Updates spectral cube test in line with angle unit corrections
Removed blob detection
Merge pull request #192 from adonath/remove_blob_detect

Removed blob detection
Add linkchecker to travis-ci sphinx build
Merge pull request #193 from cdeil/linkchecker

Add linkchecker to travis-ci sphinx build
Fix Sphinx broken link
Update astropy_helpers sub-module pointer to latest master
Merge pull request #196 from cdeil/ah-update

Update astropy_helpers sub-module pointer to latest master
Minor corrections to npred_general.py and test_spectral_cube.py
Update
Merge pull request #188 from ellisowen/issue_178_test

Add more unit tests for spectral_cube.integral_flux_image
Adds Fermi-LAT PSF data files
Adds loads script for PSF files
Adds unit tests for loading of PSF files
Adds a PSF study tutorial RST file
Adds tutorial plotting scripts for Fermi-LAT PSF study
Combined the 4 data irf files for Fermi PSF into one fits file