added discussion of 2D moment tensor sources to the manual
added another comment about 2D sources to the manual
Merge pull request #19 from komatits/devel

added another comment about 2D sources to the manual
fixed test on N_SLS when attenuation is off to use 2 instead of 1
Merge pull request #20 from komatits/devel

fixed test on N_SLS when attenuation is off to use 2 instead of 1