Made 2 tests culture-invariant.

The parse of a double is culture-dependant. In order to avoid different
results on different machines, just set a fixed culture for the tests.
Fixed bug TabCompletion in small console widths.
Fixed tests and added a test for the new fix.
Merged from upstream/master.
Merge pull request #24 from PapaMufflon/master

Fixed exception when TabCompletion tries to complete a string longer than the Console.BufferWidth.