change valid organisation code to be between 50 and 99

part of  jira story https://osraav.atlassian.net/browse/OSRA-180
OSRA-180 #code-review
changed organisation code in seeds file to match new criteria
wrote failing cucumber description for https://osraav.atlassian.net/browse/OSRA-121
Implementing Cucumber step definitions
Implement gender drop-down box for sponsors index & Cucumber step testing its presence
created factory girl instances ready for testing of filter functionality

Added number transform
Moved test into its own feature to prevent factory girl sequnces clobbering
  background table data in original feature when creating branches
Finish filter_gender steps; rename gender_filter.feature to custom_filters.feature; move filter steps into dedicated steps file
Merge pull request #97 from PurityControl/organisation_codes

change valid organisation code to be between 50 and 99
Merge pull request #99 from NikitaAvvakumov/filter_gender

Filter gender
OSRA-121 #resolve