[meta] Reduce dependencies and on-disk footprint

[ncalexan]

This is a meta ticket to track our on-disk footprint. We want to:

• reduce our dependencies, including not requiring regex
• graph our on-disk size after stripping, etc (perhaps using PerfHerder, if we can integrate against it from Travis CI/AppVeyor)

See also @thomcc's initial analysis at https://mail.mozilla.org/pipermail/sync-dev/2018-June/001661.html.

[thomcc]

I'd also argue for putting tolstoy behind #[cfg(feature = "tolstoy")] (at least until we think we want to use it in production). I think that was one the largest single change I made to reduce the size.

[ncalexan]

I'd also argue for putting tolstoy behind #[cfg(feature = "tolstoy")] (at least until we think we want to use it in production). I think that was one the largest single change I made to reduce the size.

Yep! @grigoryk's WIP at #563 includes such a feature (which we called "syncable"). We'll land that sooner rather than later.