Update at-a-glance.rst

Grammatical error

Author: duncanssmith

at-a-glance.rst

@@ -1,7 +1,7 @@
 Mink at a Glance
 ================
 
-There's huge amount of browser emulators out there, like `Goutte`_, `Selenium`_,
+There's huge number of browser emulators out there, like `Goutte`_, `Selenium`_,
 `Sahi`_ and others. They all do the same job, but do it very differently.
 They behave differently and have very different API's. But, what's more important,
 there is actually 2 completely different types of browser emulators out there: