Fix date handling (issue #251)

[pitkant]

Fixes the following error described in issue #251 by @lz1nwm:

Warning message:
In eurotime2date(x, last = TRUE) :
Unknown time code, -. No date conversion was made.

get_eurostat (and get_eurostat_json) now use eurotime2date2 function instead of the old eurotime2date function.

[codecov]

Codecov Report

Merging #256 (aaf1179) into master (3e7ad99) will not change coverage.
The diff coverage is 0.00%.

❗ Current head aaf1179 differs from pull request most recent head 30d22e6. Consider uploading reports for the commit 30d22e6 to get more accurate results

@@           Coverage Diff           @@
##           master     #256   +/-   ##
=======================================
  Coverage   67.18%   67.18%           
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  Files          24       24           
  Lines        1024     1024           
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  Hits          688      688           
  Misses        336      336           

Impacted Files	Coverage Δ
R/get_eurostat.R	52.45% <0.00%> (ø)

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