Get rid of "found = in conditional" warning

Given the latest fellowshipone-api gem being installed, I'm seeing the following warning some up:

```ruby
/Users/jhagglund/.rvm/gems/ruby-1.9.3-p484@capacityassessor/gems/fellowshipone-api-0.6.0/lib/readers/contribution_list_reader.rb:24: warning: found = in conditional, should be ==
```
That is fixed by simply indenting the statement on line 24 so it's clear that it isn't part of the conditional. Simple fix, and I did test that this change clears up the warning.