README.md in fast_excel-0.2.0 vs README.md in fast_excel-0.2.1

@@ -1,8 +1,10 @@
 # Ultra Fast Excel Writter for Ruby
 
 ```ruby
+require 'fast_excel'
+
 workbook = FastExcel.open("hello_world_ffi.xlsx", constant_memory: true)
 workbook.default_format.set(
   font_size: 0, # user's default
   font_family: "Arial"
 )
@@ -22,10 +24,12 @@
 
 for i in 1..1000
   worksheet.write_row(i, ["Hello", (rand * 10_000_000).round(2), Time.now])
 end
 
+worksheet.write_row(1001, ["Sum", FastExcel::Formula.new("SUM(B2:B1001)")], bold)
+
 workbook.close
 ```
 
 This repositiry and gem contain sources of [libxlsxwriter](https://github.com/jmcnamara/libxlsxwriter)
 
@@ -33,26 +37,26 @@
 
 1000 rows:
 ```
 Comparison:
            FastExcel:       31.7 i/s
-               Axslx:        8.0 i/s - 3.98x  slower
+               Axlsx:        8.0 i/s - 3.98x  slower
           write_xlsx:        6.9 i/s - 4.62x  slower
 ```
 
 20000 rows:
 ```
 Comparison:
            FastExcel:        1.4 i/s
-               Axslx:        0.4 i/s - 3.46x  slower
+               Axlsx:        0.4 i/s - 3.46x  slower
           write_xlsx:        0.1 i/s - 17.04x  slower
 ```
 
 Max memory usage, generating 100k rows:
 ```
 FastExcel   - 20 MB
-Axslx       - 60 MB
-write_axslx - 100 MB
+Axlsx       - 60 MB
+write_xlsx - 100 MB
 ```
 
 ## Install
 
 ```ruby