Merge pull request #371 from kpdecker/benchmarks

Add benchmark coverage for all $ APIs
Merge pull request #369 from kpdecker/reduce-intermediate

Reduce intermediate object creation
Fix bug in `siblings`

Do not consider siblings' contents when filtering
Fix bug in `prevAll`

Do not consider siblings' contents when filtering.
Implement `selector` argument of `prev` method
Fix bug in `prevUntil`

Do not consider siblings' contents when filtering.
Implement `selector` argument of `next` method
Fix bug in `nextAll`

Do not consider siblings' contents when filtering.
Fix bug in `nextUntil`

Do not consider siblings' contents when filtering.
more keywords
it's -> its

Can't get any more trivial than that
Merge pull request #379 from dandv/patch-1

it's -> its
pin entities to <0.4
Merge pull request #382 from globin/pin-entities

pin entities to <0.4
Optimize filter with selector

Test: traversing - Parent (file: jquery.html)
  cheerio x 8,651 ops/sec ±11.22% (62 runs sampled)
  jsdom x 6,835 ops/sec ±12.34% (68 runs sampled)
  old x 442 ops/sec ±10.25% (65 runs sampled)
  Fastest: cheerio

Test: traversing - Parents (file: jquery.html)
  cheerio x 25.36 ops/sec ±17.24% (36 runs sampled)
  jsdom x 101 ops/sec ±13.70% (57 runs sampled)
  Fastest: jsdom

Test: traversing - Closest (file: jquery.html)
  cheerio x 58.91 ops/sec ±13.71% (55 runs sampled)
  jsdom x 126 ops/sec ±13.47% (63 runs sampled)
  old x 6.35 ops/sec ±14.50% (21 runs sampled)
  Fastest: jsdom

Test: traversing - Filter (file: jquery.html)
  cheerio x 5,497 ops/sec ±14.45% (54 runs sampled)
  jsdom x 6,233 ops/sec ±18.27% (56 runs sampled)
  old x 179 ops/sec ±42.74% (48 runs sampled)
  Fastest: jsdom

Test: traversing - Children (file: jquery.html)
  cheerio x 1,627 ops/sec ±14.94% (50 runs sampled)
  jsdom x 243 ops/sec ±16.94% (51 runs sampled)
  old x 217 ops/sec ±12.39% (54 runs sampled)
  Fastest: cheerio
Add html rendering bench case
Simplify attribute rendering step

Removes the keyscan used to determine the size of the object.
Cache tag check in render
Remove unnecessary encoding step for attrs
Add css benchmark case