.gitignore: add IDEA's *.iml
pom.xml: remove jersey-core dependency

Only the annotations are needed.
pom.xml: exlude jackson-{databind,core} from jackson-module-jsonSchema

json-schema-core provides more recent versions.
pom.xml: update json-schema-core dependency

It is now up to 1.0.1.
Merge pull request #16 from fge/master

Dependencies updates, and add one element to .gitignore