Build HTTP queries with '&'

This fixes #4.
Add details about request failures to the exception message

This fixes #7.
Set higher timeout for functional test

Tests were randomly failing because of timeouts, while there were no
technical problems on our side.
Add __toString function to the TranslationMatch class

This fixes #8.
Add phpunit/phpunit as a dependency

This fixes #9
Add quality badges

This fixes #10 [skip ci]