Formalize API for removing derivatization in IUPAC

Also refactored test suite infrastructure using
pytest

.travis.yml

@@ -12,8 +12,9 @@ cache: pip
 # command to install dependencies
 install:
   - pip install -U setuptools
+  - pip install pytest
   - pip install cython
   - pip install -e .[plot,glyspace]
   # - pip install -r requirements.txt
 # command to run tests
-script: nosetests
+script: make test

glypy/composition/glycan_composition.py

@@ -988,3 +988,11 @@ def extend(self, *args):
 
 class FrozenError(ValueError):
     pass
+
+
+class HashableGlycanComposition(FrozenGlycanComposition):
+    def __hash__(self):
+        return hash(str(self))
+
+    def __eq__(self, other):
+        return str(self) == str(other)

makefile

@@ -2,10 +2,11 @@ all: develop test docs
 
 
 test:
-	nosetests --with-coverage --with-timer --cover-package=glypy --cover-html --cover-html-dir=test_reports --logging-level=DEBUG -v --with-id glypy/tests/
+	py.test -v  glypy --cov=glypy --cov-report html --cov-report term
 
 retest:
-	nosetests --cover-package=glypy --logging-level=DEBUG -v --with-id --failed glypy/tests/
+	py.test -v glypy --lf
+
 clean:
 	@rm  glypy/*/*.pyd
 	@rm  glypy/*/*.so
@@ -17,4 +18,4 @@ develop:
 	python setup.py develop
 
 serve-docs:
-	python -m webbrowser -n docs\build\html\index.html
+	python -m webbrowser -n docs/build/html/index.html