Fix regexes that break Leaflet inside a multi line comment block, fixes #1288

[kristerkari]

This is a fix for issue #1288.

Currently the */ characters inside Leaflet's regular expressions break multi line comment blocks that can be used for lazy evaluating javascript [source 1] [source 2].

In addition to working around the regular expressions, I have also added L.Util.trim which with these changes is used by L.Util.splitWords and L.DomUtil.removeClass. If adding trim method is a problem, I can provide an alternative workaround.

trim and removeClass methods are the same ones used in Pikaday.js:
https://github.com/dbushell/Pikaday/blob/master/pikaday.js#L73

List of changes:

1. Added L.Util.trim method.
2. Changed L.Util.splitWords to call L.Util.trim.
3. Replaced L.DomUtil.removeClass with a new one to avoid having a regular expression with */. Also uses L.Util.trim.
4. Added parentheses around the regular expression in Path.VML.js to avoid having a regular expression with */.

Linting and tests:

Checking for JS errors...
    Check passed
................................................................................
................................................................................
....................................
PhantomJS 1.9 (Mac): Executed 196 of 196 SUCCESS (1.393 secs / 0.727 secs)

Let me know if any changes are needed.

[mourner]

Looks pretty good! Thanks!