Add support for ignoring diacritics; Use <mark> tags for highlighting

[Dentosal]

Sorry to introduce two changes in the same PR. I also fixed some deprecation warnings with React by moving to React.createElement style. If this is a real problem, feel free to either modify it yourself or ask me to do it in comments.

This PR adds two props: ignoreDiacritics and diacriticsBlacklist. The code uses unicode normalization to separate and combine diacritical marks from characters.

ignoreDiacritics

ignoreDiacritics allows ignoring diacritical marks when matching. For instance cafe will match café and á will match a. Currently both search and subject are simplified, so it is not possible to make á not match a, except when using diacriticsBlacklist.

diacriticsBlacklist

diacriticsBlacklist contains a list of characters excluded from diacritics removal. For example:

<Highlight
  search='Café Ääkkönen'
  ignoreDiacritics=true
  diacriticsBlacklist='ÄäÖö'
>

Will match Cafe Ääkkönen and café ääkkönen but not cafe aakkonen.

[coveralls]

Changes Unknown when pulling b1e281f on Dentosal:master into ** on helior:master**.

[coveralls]

Changes Unknown when pulling ba937ab on Dentosal:master into ** on helior:master**.

[helior]

This is a rad feature @Dentosal, thanks for your contribution! I'll give this a review sometime during the long-weekend.

[Dentosal]

@helior Any problems with this? Feel free to ask if there are any issues.

[helior]

@Dentosal no issue with these changes, other than the current merge conflicts; also, I haven't tested this locally. If you want to make the updates I'll merge when they're ready, otherwise I'll have to put some time aside to button this up and get it merged. A lot of people will appreciate this contribution, thanks again!

[ericgio]

The use of normalize pretty much excludes IE. This solution is more widely cross-browser compatible.

[pasieronen]

@helior I've rebased @Dentosal's changes on top of the current master (with some commit squashing/splitting), and tested the result with our app. I left normalize as is - if you need IE11 support, you can use a polyfill for that.

[pasieronen]

@helior Is there something you'd like to see changed before merging this?