Support latest version of pkg:csv (flutter#6)

Author: kevmoo

pubspec.yaml

@@ -1,5 +1,5 @@
 name: term_glyph
-version: 1.0.1
+version: 1.0.2-dev
 
 description: Useful glyphs and Windows-safe equivalents.
 author: Dart Team <[email protected]>
@@ -9,6 +9,6 @@ environment:
   sdk: '>=1.8.0 <3.0.0'
 
 dev_dependencies:
-  csv: ^3.0.0
+  csv: '>=3.0.0 <5.0.0'
   dart_style: '>=0.2.0 <2.0.0'
   test: '>=0.12.0 <2.0.0'