Escapes the URL before adding document

[antitoine]

Allow using Unicode character in the document ID (in CouchDB). Without this escape function, the following error occurs:

{"name":"couch2elastic4sync","hostname":"zbra","pid":21052,"level":30,"msg":"putting to http://localhost:9200/test/idx/\u0000idea\u0000588e5501d4c2af7879798180ada017460c757b91f44751bcc10d164201a16346\u0000","time":"2019-03-20T15:26:37.650Z","v":0}
_http_client.js:137
      throw new TypeError('Request path contains unescaped characters');
      ^

TypeError: Request path contains unescaped characters
    at new ClientRequest (_http_client.js:137:13)
    at Object.request (http.js:39:10)
    at Req._send (/home/ancha/.nvm/versions/node/v8.15.1/lib/node_modules/couch2elastic4sync/node_modules/jsonist/node_modules/hyperquest/index.js:136:21)
    at /home/ancha/.nvm/versions/node/v8.15.1/lib/node_modules/couch2elastic4sync/node_modules/jsonist/node_modules/hyperquest/index.js:50:21
    at _combinedTickCallback (internal/process/next_tick.js:132:7)
    at process._tickCallback (internal/process/next_tick.js:181:9)