Merge pull request #208 from chrislonng/master

comment contains some misspell

prometheus/http.go

@@ -61,13 +61,13 @@ func nowSeries(t ...time.Time) nower {
 // Note that InstrumentHandler has several issues:
 //
 // - It uses Summaries rather than Histograms. Summaries are not useful if
-//   aggregation accross multiple instances is required.
+//   aggregation across multiple instances is required.
 //
-// - It uses microseconds as unit, which is deprecated and should be reploced by
+// - It uses microseconds as unit, which is deprecated and should be replaced by
 //   seconds.
 //
 // - The size of the request is calculated in a separate goroutine. Since this
-//   calculatior requires access to the request header, it creates a race with
+//   calculator requires access to the request header, it creates a race with
 //   any writes to the header performed during request handling.
 //   httputil.ReverseProxy is a prominent example for a handler
 //   performing such writes.