Skip attribute macros

fixes #10 - prevents attribute macros being transformed in the token stream

Ignore keywords during transformations

After this patch rust keywords will not have case transformations applied

// before patch
upper!(fn test(){}); // render `FN TEST() {}`

// after patch
upper!(fn test(){}); // render `fn TEST() {}`

0.3.1

Fix pascal! marco to handle SHOUTY_CASE transforms

0.3.0

Target stable rust
#[proc_macro_hygiene] feature stabilzed in rust 1.45.0 and is no longer required to use this crate
Removed use of #[pattern] feature