Minor tests refactoring

Improved the ping API route, and updated in consequences some unit tests in the api.test.js suite.
Fixed #70: Some issues with URL solving

1. The default solve RegExp has been fixed for cases such as ':toto:tutu'
2. The value of solver.lastIndex is now updated relatively to the lengths of the two related strings. That fixes cases such as { someQuiteLongStrings: "aShorterOne" }.