Swap out sift3 for swift4 common

[thatguyintech]

Fix #113

From Siderite's blog:

After implementing Sift4, I can now tell you that the simple version is slightly better than Sift3 for small maxOffset values like 5, but it gets better as the value increases. The common version is a bit more complex, but the error decreases with 33% and maintains a low error for large maxOffset values.

I pretty much just copied over the source. I took out the maxDistance for simplicity, and set a default maxOffset of 5 for consistency.

[thatguyintech]

@derrickko any thoughts on this?

[derrickko]

@alberthu16 looks awesome. Did you update the tests to make sure they pass?

[thatguyintech]

Thanks @derrickko! Actually, I didn't have to update the tests to make sure they pass. None of them broke, so I'm assuming the functionality is consistent. Should I add some more domain checks? There are no tests for the actual edit distance algorithm currently.

[thatguyintech]

@derrickko thoughts on adding tests or leaving as is?