DataArray::hasData() is now declared const (see issue #173)
Merge pull request #178 from jgrewe/const_has_data

DataArray::hasData() is now declared const (see issue #173)

LGTM
Value: call default constructor in copy constructor

This will properly construct the value object before we call
assign_variant_form(), which in turn will call set<T>() which will
call maybe_deallocte_string() and therefore access the dtype
member variable. The latter therefore has to be properly
initialised.
Merge pull request #182 from gicmo/ValueCopyCtor

Value: call default constructor in copy constructor
Value: Initialise uncertainty (double) to 0.0

This fixes the valgrind warning in TestDataSet::testValueIO:
"Syscall param write(buf) points to uninitialised byte(s)"
See issue #180
[test] Change tests of optional<T> to use operator bool()

This is part one of the fix for the build on osx, issue #181.
ImplContainer: Add operator!=(bool b)

We already had operator==(bool b). This is part two of the fix for
the build on osx, issue #181.
Merge pull request #184 from gicmo/osxBuild

Fix build on OSX. Closes issue #181
Merge pull request #183 from gicmo/ValueDoubleInit

Value: Initialise uncertainty (double) to 0.0