Make file URLs in error output more user friendly.

[edhager]

Fixes #952.

This PR makes URLs contained in errors printed to the browser console more user friendly by doing two things:

1. Spaces are added around the URL so the browsers do not include the ">" as part of the URL:

   at regular suite  < http://localhost:9000/_tests/tests/unit/lib/reporters/Html.js:87:21 >
   

   With this change, clinking on the link does the following:

   • Chrome opens the file at the designated line number in the "Sources" tab in the development tools.
   • Safari, opens the file at the designated line number in the "Resources" tab in the development tools.
   • Firefox tries to open the file in a new tab. Without the next change, this request fails.
   • IE and Edge do nothing because they do not turn the URL into a hyperlink.

2. To support the request that Firefox makes when the URL is clicked in the console, a URL filter was added to the server code to remove the line and column number references so the request is handled properly.

[codecov-io]

Codecov Report

Merging #969 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #969      +/-   ##
=========================================
+ Coverage   92.68%   92.7%   +0.01%     
=========================================
  Files          58      59       +1     
  Lines        4595    4605      +10     
  Branches      998     999       +1     
=========================================
+ Hits         4259    4269      +10     
  Misses        336     336

Impacted Files	Coverage Δ
src/lib/Server.ts	78.61% <100%> (+0.27%)	⬆️
src/lib/middleware/filterUrl.ts	100% <100%> (ø)
src/lib/common/ErrorFormatter.ts	95.28% <100%> (ø)	⬆️

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[jason0x43]

Finally got a chance to look at this. In my own tests, it seems to work as described -- great!

I agree, though, that the spaces seem less than ideal. What if we used a format more like Chrome's for the locations, like

at regular suite @ http://localhost:9000/_tests/tests/unit/lib/reporters/Html.js:87:21

The <> were originally used so the output would look similar to browser stack listings. However, browsers seem to have adopted simpler formats at this point.

[edhager]

@jason0x43 I updated the code to use @ instead of < >.