Added requirements.txt to MANIFEST.in (to ensure is included in pip release)
Added requirements.txt to MANIFEST.in (to ensure is included in pip release)

barseghyanartur/django-rest-framework-gis,pglotov/django-rest-framework-gis,nmandery/django-rest-framework-gis,bopo/django-rest-framework-gis,djangonauts/django-rest-framework-gis,manhg/django-rest-framework-gis,arjenvrielink/django-rest-framework-gis,illing2005/django-rest-framework-gis,sh4wn/django-rest-framework-gis,nmandery/django-rest-framework-gis