chore(api): restore the OrFail method to the Assertion interface (#25)

This change restores API compatibility by restoring the `OrFail()`
method to the `Assertion` interface, and marking it as deprecated in
favor of the new `Now()` method.

Signed-off-by: Arik Kfir <arik@kfirs.com>

asserter.go

@@ -108,10 +108,12 @@ func (a *asserter) Will(m Matcher) Assertion {
 }
 
 type Assertion interface {
-
 	// Now will perform the assertion and fail immediately if it mismatches.
 	Now()
 
+	// Deprecated: OrFail is a synonym for Now.
+	OrFail()
+
 	// For will continually perform the assertion until the given duration has passed or until it mismatches. If it
 	// mismatched once, the assertion is considered failed.
 	For(duration time.Duration, interval time.Duration)
@@ -132,6 +134,17 @@ type assertion struct {
 	desc      string
 }
 
+//go:noinline
+func (a *assertion) OrFail() {
+	GetHelper(a.t).Helper()
+	if a.evaluated {
+		panic("assertion already evaluated")
+	} else {
+		a.evaluated = true
+	}
+	a.matcher.Assert(a, a.actuals...)
+}
+
 //go:noinline
 func (a *assertion) Now() {
 	GetHelper(a.t).Helper()