Changed macros to work on stable (with proc-macro-hack)

[danielhenrymantilla]

proc-macro-hack-based (much simpler) reimplementation of #148, to address #106

[sfackler]

@dtolnay is the missing documentation warning expected?

[dtolnay]

Yes, you have to write the documentation. ;)

/// ...
#[cfg(feature = "macros")]
#[proc_macro_hack]
pub use phf_macros::phf_map;

...

[Speedy37]

What is blocking you from merging this and stabilizing it?

[abonander]

LGTM minus the version number edits.

[danielhenrymantilla]

Reverted the version bump, rebased on master, and added some documentation on the macros.

Also added a field in Cargo.toml to ensure that the macros documentation appears on https://docs.rs.

Remaining question: should the "macros" feature by enabled by default? I haven't done it, but except maybe for compatibility with older rustc compilers, I can't see a reason for them no to be enabled by default, given that they are stable.

[abonander]

We've technically bumped the minimum to 1.31 now but that's mostly to use const fn on stable with unicase. Upgrading siphasher apparently needed a new minimum version but I'm not sure what it was. So macros on by default should be fine; I'd say we could remove the feature flag entirely but if people aren't going to use it then they might as well be able to turn it off to save a little bit of compile time.

[abonander]

I can make that change myself, thanks for your contribution!

[danielhenrymantilla]

I'm glad I could help. Now updating the README.md would be a good thing to do :)

[abonander]

Yep.