More work on parsing control files.

debian_package.py:
* Strip relationship strings when parsing them.
* Added parsing for Standards-Version
* Added parsing for Build-Depends et. al

debian_package_test.py:
* Created DebianPackageTestCase as a base test case. Contains extra
  equality assertion functions. Subclassed the relevant tests from here.
* Tests parsing of standards version (needs improvement)
* Added some tests for parsing Build-Depends. After writing the function
  I discovered that I need more.
* Test import_control_file on a valid file.
Merge branch 'master' of https://github.com/lengau/debalot
Updated README about getting involved.
Merge branch 'master' of https://github.com/lengau/debalot