Add build, update, and release instructions in the README.md (#545)

README.md

diff --git a/README.md b/README.md
index 02c188b..63416cd 100644
--- a/README.md
+++ b/README.md
@@ -6,3 +6,70 @@
 Enterprise Integration Patterns with powerful bean integration.
 
 This project provides Apache Karaf support for Apache Camel.
+
+## Build
+
+To build camel-karaf, simple do:
+
+```
+mvn clean install
+```
+
+If you want to skip the tests, you can do:
+
+```
+mvn clean install -DskipTests
+``` 
+
+## Upgrade
+
+If you want to upgrade camel-karaf to a new camel version, here's the process:
+
+1. camel repository has to be cloned in the same folder as camel-karaf repository:
+
+```
+git clone https://github.com/apache/camel
+```
+
+2. in the camel repository, you have to checkout on the target version tag:
+
+```
+cd camel
+git checkout camel-x.y.z
+```
+
+3. once you have built camel-karaf, you can find the update tool in `tooling/camel-upgrade` folder. Go in this folder:
+
+```
+cd tooling/camel-upgrade
+```
+
+4. you can now run the upgrade tool:
+
+```
+java -jar target/camel-upgrade-*.jar
+```
+
+5. When done, you can review the changes (with `git diff` for instance) and create a Pull Request.
+
+## Release
+
+Here's the process to do a camel-karaf release:
+
+1. Create the release tag:
+
+```
+mvn release:prepare
+```
+
+2. Push the release:
+
+```
+mvn release:perform
+```
+
+3. Close the Maven staging repository on repository.apache.org
+
+4. The source distribution is available the `target` folder: `camel-karaf-x.y.z-source.release.zip.*`. You have to stage the source distribution files to `svn://dist.apache.org/repos/dist/dev/camel`.
+
+5. When both Maven Staging Repository (closed) and dist.apache.org are up to date with the release files, you can start the release vote.