Fix github-linguist statistics (#547)

* Added .gitattributes

Tell git that the test/testdata/ files and Jupyter Notebooks are binary
files, ie. do not display diffs and do not touch line endings in those
files.

* Moved 'CQ examples.ipynb' to examples directory

Now github-linguist will classify it as documentation, and the massive
line count in that file will stop skewing the language statistics for
CadQuery on Github.

Author: marcus7070

.gitattributes

@@ -0,0 +1,6 @@
+# Don't display text diffs for files that are not human readable
+# Git should not modify line endings in these test files
+tests/testdata/* -diff -text
+
+# Jupyter notebooks should be classified as documentation
+*.ipynb linguist-documentation -diff -text