Fix Travis no_std test and remove old Cargo patch

Note: Cargo patch was used since rand_os dependend on
rdrand on sgx. Now getrandom has its own rdrand impl.

Author: dhardy

.travis.yml

@@ -268,7 +268,7 @@ before_install:
 
 script:
   - cargo test --tests --no-default-features
-  - cargo test --no-default-features --features getrandom
+  - cargo test --tests --no-default-features --features getrandom
   # TODO: add simd_support feature:
   - cargo test --features=serde1,log
   - cargo test --examples

Cargo.toml

@@ -91,6 +91,3 @@ autocfg = "0.1"
 
 [package.metadata.docs.rs]
 all-features = true
-
-[patch.crates-io]
-rand_core = { path = "rand_core", version = "0.5" }