Converter should not require local locale settings

[chad-earthscope]

The converter requires being executed in a locale of C (or en_US.UTF-8 seems to work also):
https://github.com/iris-edu/stationxml-seed-converter#system-language-requirments

This effects the conversion between two formats, the encodings of which the user has no control over. Since the formats are fixed to specific encoding and number usage it makes sense to treat them as such in the converter, whatever the caller's locale is should not matter.

P.S. For this converter, where a users locale makes sense would be on input, like command line parameters. But I don't see any that take numbers and text should be assumed to be UTF-8.

[chad-earthscope]

As an example, experiences and wasted time reporting and diagnosing such as in #63 could be avoided.