Fix ci build fails

There was some problem with the std examples, so I changed ci to only check a seperate use of the bme680 in a new ci-folder to be no_std compatible.

.gitignore

@@ -1,3 +1,5 @@
 Cargo.lock
-/target
+**/target
 **/*.rs.bk
+
+

.travis.yml

@@ -6,7 +6,7 @@ rust:
 script:
   - cargo build --verbose
   - cargo test --verbose
-  - cargo check --target thumbv7m-none-eabi # check for no_std
+  - cd ci/no_std_test && rustup target add thumbv7m-none-eabi && cargo check --target thumbv7m-none-eabi # check for no_std
 matrix:
   allow_failures:
     - rust: nightly

ci/no_std_test/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "no_std_test"
+version = "0.1.0"
+authors = ["marcelbuesing <buesing.marcel@googlemail.com>"]
+edition = "2018"
+
+[dependencies]
+bme680 = { path = "../../"}
+log = "0.4"

ci/no_std_test/src/lib.rs

@@ -0,0 +1,8 @@
+#![no_std]
+
+use bme680::*;
+use log::info;
+
+pub fn test_no_std() {
+    info!("chipid {:?}", BME680_CHIP_ID);
+}