added documentation on the evaluate_script method

README.rdoc

@@ -119,6 +119,10 @@ Querying:
     find_button
     field_labeled
 
+Scripting:
+
+    evaluate_script – Returns the value of the executed javascript (only works on javascript supported drivers)
+
 Debugging:
 
     save_and_open_page
@@ -158,7 +162,7 @@ For ultimate control, you can instantiate and use a session manually.
 Capybara does not try to guess what kind of selector you are going to give it,
 if you want to use CSS with your 'within' declarations for example, you'll need
 to do:
-    
+
     within(:css, 'ul li') { ... }
 
 Alternatively you can set the default selector to CSS, which may help if you are
@@ -233,4 +237,4 @@ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.