Make regex a feature of this crate, passed through to env_logger

This allows to deactivate the feature if wanted.

env_logger comes with several optional-but-default-activated features,
including a dependency on regex. Not everyone likes to pull in regex.
Putting this behind a feature allows users of android_logger to use it
with default-features=false and thus removing the regex dependency.

Author: badboy

Cargo.toml

@@ -11,6 +11,10 @@ A logging implementation for `log` which hooks to android log output.
 keywords = ["android", "bindings", "log", "logger"]
 categories = ["api-bindings"]
 
+[features]
+default = ["regex"]
+regex = ["env_logger/regex"]
+
 [dependencies]
 lazy_static = "1.0"