remove asserts from kowhai_utils

some platforms don't implement all the std signal lib required to use
assert (like _exit, _kill, etc), it would be nice if kowhai didnt depend
on any of these ... it seems these asserts may just have been left there
for development anyway so I think it is safe enough just to remove them
since they are all on internal (static) functions and assume they wont
happen
Merge branch 'master' into kowhai_utils_asserts
Merge pull request #9 from othane/kowhai_utils_asserts

Kowhai utils asserts