Point submodule remotes to https address

Previously the two git submodules (json11 & CppSQLite) were pointing to
GitHub repos via SSH (git@github.com…), but accessing these repos
requires publickey access (i.e., repo membership). Updating submodules
would result in the following error:

    Cloning into 'deps/CppSQLite'...
    Permission denied (publickey).
    fatal: Could not read from remote repository.

    Please make sure you have the correct access rights
    and the repository exists.
    Clone of 'git@github.com:neosmart/CppSQLite.git' into submodule path 'deps/CppSQLite' failed

Using GitHub's https protocol fixes the problem.

Once these changes are pulled in, make sure you update your working
copy:

    git submodule sync
Merge pull request #13 from andrewsardone/submodule-remotes

Merge pull request #13