disable perf and unicode features for regex

[justinrlle]

The last version of regex exposes now more features to help reduce bloat/binary size. You can read the full announcement here: rust-lang/regex#613
I've disabled the perf and unicode features, dividing by two the overhead of regex, and removing 4 dependencies.
I've got the following results for binary size:

• without regex: 2.8M (539k stripped)
• with regex v1.2: 4M (1.7M stripped)
• with regex v1.3 with only std feature: 3.2M (903K stripped)

[RazrFalcon]

Nice.

Rust technically allows non-Latin identifiers, but I'm not sure anyone actually uses them.