Clear previous search and hash on push/replace with pathname only

[sachmata]

When history.push or history.replace is called with string URL without search or hash part the ones from previous location are kept.

history.push('https://reacttraining.com/with-query?query=hello');

// https://reacttraining.com/with-query?query=hello -> This is OK
console.log(history.createHref(history.location));

// new route is pushed without search
history.push('https://reacttraining.com/no-query');

// https://reacttraining.com/no-query?query=hello -> Current result keeps the old search
console.log(history.createHref(history.location));

This change adds default empty values for search and hash which are replaced if parsePath function finds some.

If the previous search or hash have to be reused PartialPath object can be passed with omitted keys.

[jaydenseric]

Fixes #814 ?

[sachmata]

Fixes #814 ?

Yes, I have missed that is already reported.

[Hypnosphi]

@mjackson can you please review?