Meta tag regex update

I found a couple of bugs in the regex causing some strings to work or fail when they shouldn't. I noticed this when using Parse's AppLinks Cloud Module.

i.e. <meta property="moo" content="sauce" > matches (good)
     <meta property="moo" content="sauce"> does not match (not good)
     <metaproperty="moo" content="sauce" > matches (not good)

Moves the space check from after the attribute to before it

I understand that you've got an issue open to improve the matching system (to solve issues like <!-- or -->), however this is a quick fix that'll provide support to Parse's AppLinks Cloud Module and other standard meta tags which are being missed out. It could save some people from a lot of the strife that I just went through.