Add test to exercise curl code.

This is a very simple test that opens a url, the github status api, and
verifies the FS type is correct.
Update .skipif logic to support "does not contain" operator.

Add new operator, >= (as opposed to <=), which mean <variable> does not contain
the substring <value>. For example, adding this line,
"CHPL_AUX_FILESYS >= lustre", to a skipif means: skip the test if
CHPL_AUX_FILESYS does not contain the substring "lustre".

I am not really happy with the operator, but I don't think it is any more or
less confusing than the <= operator.
Update skipifs for lustre and curl tests.