Added XRegExp.join() which joins an Array with the given separator into a single XRegExp

Split the majority of XRegExp.union into a private prepareJoin() helper.
Added XRegExp.join() which joins an Array with the given separator into
a single XRegExp.
Updated XRegExp.union() to use new XRegExp.join() internally.
Rebuilt the xregexp-all.js file.
Minor.
Update Unicode data files now that v6.2.0 is finalized.
Fix edge case where cache lookup could allow slash as flag.
Minor.
Minor.
Fixed bug with duplicate group name

If you used the same group name multiple times, previously, it would have just used the value stored in the last group (even if it failed to find that group).

Now it will only use the last successfully found group.
Added component.json. Fixes #48
Allow for usage in meteor 0.6.5 and higer

For meteor 0.6.5 and higher, the used library files must explicitly define a global (e.g. there must be no var prefix)
Update to Unicode v6.3.0 data

Closes #57.
Merge remote-tracking branch 'remotes/ggpeters/master'
Merge remote-tracking branch 'remotes/KylePDavis/master'
Merge remote-tracking branch 'remotes/joscha/patch-1'
Merge remote-tracking branch 'remotes/mathiasbynens/update-unicode'