Merge pull request #93 from rust-bitcoin/2019-0.12.1

bump version to 0.12.1

CHANGELOG.md

+# 0.12.1 - 2019-01-15
+
+* Minor bug fixes
+* Fixed `cc` crate version to maintain minimum compiler version without breakage
+* Removed `libc` dependency as it our uses have been subsumed into stdlib
+
 # 0.12.0 - 2018-12-03
 
 * **Overhaul API to remove context object when no precomputation is needed**

Cargo.toml

 [package]
 
 name = "secp256k1"
-version = "0.12.0"
+version = "0.12.1"
 authors = [ "Dawid Ciężarkiewicz <dpc@ucore.info>",
             "Andrew Poelstra <apoelstra@wpsoftware.net>" ]
 license = "CC0-1.0"