Support for custom separator.

Conflicts:
	pom.xml
Missing final modifier.
Support for trimming values
Support for XML files with repeated element. Values can be joined into single value.
Usage instruction updated
Readme updated.
Changelog updated.
Support for handling any XML document.
Usage instruction updated.
Validating command line arguments.

Conflicts:
	src/main/java/com/fordfrog/xml2csv/Main.java
release 1.2.0