Fix typos and grammatical errors

I've been having some issues with my JDK and encountered the following message while building:
```
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.14.1:test (default-test) on project logback-core: Execution default-test of goal org.apache.maven.plugins:maven-surefire-plugin:2.14.1:test failed: The forked VM terminated without saying properly goodbye. VM crash or System.exit called ?
[ERROR] Command was/bin/sh -c cd /usr/home/ecd/repos/misc/logback/logback-core && /usr/local/linux-sun-jdk1.7.0/jre/bin/java -jar /usr/home/ecd/repos/misc/logback/logback-core/target/surefire/surefirebooter6720085623583714622.jar /usr/home/ecd/repos/misc/logback/logback-core/target/surefire/surefire846998716577511588tmp /usr/home/ecd/repos/misc/logback/logback-core/target/surefire/surefire_08386594812885878010tmp
[ERROR] -> [Help 1]
```
The ```without saying properly goodbye``` and the ```Command was/bin/sh``` caught my attention. This pull requests fixes those plus some other typos.