Run build and tests for no_std in Travis.

There are no tests for no_std mode yet.

.gitignore

@@ -5,3 +5,4 @@ tokamak.toml
 .idea
 *.iml
 examples/ferris.cbor
+.cargo/config

.travis.yml

@@ -10,7 +10,10 @@ matrix:
 sudo: false
 before_script:
   - rustup component add rustfmt
+  - rustup target add thumbv7em-none-eabihf     # Any target that does not have a standard library will do
 script:
   - cargo fmt --all -- --check
   - cargo build
   - cargo test
+  - cargo build --no-default-features --target thumbv7em-none-eabihf # Test we can build a platform that does not have std.
+  - cargo test --no-default-features --lib --tests # Run no_std tests

tests/ser.rs

@@ -1,11 +1,10 @@
-use std::collections::BTreeMap;
-
 #[cfg(feature = "std")]
 mod std_tests {
     use serde::Serializer;
     use serde_bytes::{ByteBuf, Bytes};
     use serde_cbor::ser;
     use serde_cbor::{from_slice, to_vec};
+    use std::collections::BTreeMap;
 
     #[test]
     fn test_string() {