no files named memory: please
correct all the /memory:
fix all but one of the test fails
add a test for using sqlite with an absolute path

the first forward slash is always present because of how url parsing
works. because it may be confusing, add a test for how to specify an
absolute path (requires an extra forward slash).
3 slashes are required for :memory:

otherwise it's misunderstood to be an unconventional hostname
Merge pull request #5075 from AD7six/3.0-travis-fix

no files named "memory:" please