Add vanillawxr, wxr to supported export types (fixes #13)

[dac514]

• Add vanillawxr, wxr to supported export types (fixes Not all file types are Submitted #13)
• Update coding standards

[greatislander]

Looks like the Travis matrix needs to be updated to use PHP 7.1 and 7.2 instead of 7.0 and 7.1.

[codecov]

Codecov Report

Merging #17 into dev will decrease coverage by 0.08%.
The diff coverage is 0%.

@@             Coverage Diff              @@
##                dev      #17      +/-   ##
============================================
- Coverage     32.45%   32.37%   -0.09%     
  Complexity      223      223              
============================================
  Files            11       11              
  Lines           801      803       +2     
============================================
  Hits            260      260              
- Misses          541      543       +2

Impacted Files	Coverage Δ	Complexity Δ
inc/class-admin.php	85.22% <ø> (ø)	25 <0> (ø)	⬇️
inc/dspace/class-deposit.php	0% <ø> (ø)	39 <0> (ø)	⬇️
inc/protocol/swordv1/class-entry.php	0% <0%> (ø)	16 <0> (ø)	⬇️
inc/protocol/swordv1/class-errordocument.php	0% <0%> (ø)	6 <0> (ø)	⬇️
inc/dspace/class-admin.php	2.52% <0%> (-0.05%)	41 <0> (ø)
inc/protocol/swordv1/class-workspace.php	0% <0%> (ø)	8 <0> (ø)	⬇️

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