Test if a trace that fits perfectly into a gap in another trace can be added
modify test, test both methods 0 and 1 for Trace.__add__(), I think they
both should behave the same in this case. Also check that output is a
normal array (no masked array)
fix merging in valid data into masked data.

checking of equality has to be done differently to respect the special
cases involved with masked data.
changelog
credits
Test if dtype remains the same after randomly adding to a trace
convert back to original data's dtype
correct test, now actually fails because of a masked array
after Trace.__add__(): check if we can downgrade to ndarray if we have a
masked_array.
Merge branch 'master' into 638

Conflicts:
	CHANGELOG.txt
Merge pull request #638 from olstar/master

Test if a trace that fits perfectly into a gap in another trace can be a...