First release

Last changes for first public version. Closes #11 (closed).

After merging:

1. Tag that merge commit.
2. Create a release and attach source and binary builds of the package.
3. Tell N. how to download the newest version and how to cite it. Or better: Just send him the package so that he uses the correct version before all that refactoring.
4. Merge into v2.0.

.Rbuildignore

@@ -4,3 +4,4 @@
 ^\.Rproj\.user$
 ^LICENSE\.md$
 ^Notizen\.md$
+^LICENSE\.txt$