tests/wkb_test:

Renamed and clarified (comments) the 3d point wkb dumps test case.
tests/wkb_test:

Removed an unnecessary test case.
tests/wkb_test:

Split PointTestCase and LineStringTestCase classes into separate
classes for `dumps` and `loads`.
tests/wkt_test:

Split PointTestCase and LineStringTestCase classes into separate
classes for `dumps` and `loads`.
tests/wkb_test:

Renamed test_dumps_linestring_z to test_dumps_linestring_3d.
tests/wkb_test:

Removed `test_dumps_linestring_m`.
tests/wkb_test:

Renamed `test_dumps_linestring_zm` to `test_dumps_linestring_4d` and
implemented the test case.
.travis.yml:

Added build config for travis-ci.