Unpin requirements.
Unpin requirements.

Previously, requirements in `pip-requirements.txt` where pinned to an
exact version (e.g. `requests==1.1.0`). This causes problems when
other CKAN-related packages (e.g. core CKAN or another extension) has
the same requirement but with a different version. Therefore, only the
minimally required version should be specified (e.g. `requests>=1.1.0`).

pduchesne/ckanext-geoview,singularita-corp/ckanext-geoview,pduchesne/ckanext-geoview,taijiang-tw/ckanext-geoview,singularita-corp/ckanext-geoview,singularita-corp/ckanext-geoview,ckan/ckanext-geoview,ckan/ckanext-geoview,kalxas/ckanext-geoview,ckan/ckanext-geoview,kalxas/ckanext-geoview,taijiang-tw/ckanext-geoview,kalxas/ckanext-geoview,taijiang-tw/ckanext-geoview,pduchesne/ckanext-geoview