Post 1.0.0 issues

[danthorpe]

• Remove the documentation coverage badge? CocoaDocs still doesn't seem to be working, I think an underlying issue with Jazzy - as I can't generate them locally either.

• There are some incorrectly named unit test functions which might be confusing, especially in the FX stuff.

• Spelling errors in the README.

• Would make sense to provide access to FXQuote and for it to conform to NSCoding. e.g. something like

  Yahoo<USD,EUR>.quote(100) { result in
      if let quote, euros = result.value {
          // have access to the quote and the euros.
      } 
   }

[codecov-io]

Current coverage is 100.00%

Merging #16 into development will not affect coverage as of 728fd9e

@@            development     #16   diff @@
===========================================
  Files                 8       8       
  Stmts               457     466     +9
  Branches              0       0       
  Methods                               
===========================================
+ Hit                 457     466     +9
  Partial               0       0       
  Missed                0       0       

Review entire Coverage Diff as of 728fd9e

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