Name(egg) != Directory(egg) on the filesystem

For example an egg might be refered to as 'cython' and placed on the
filesystem as 'Cython' (titled). And for cython-zstd it is placed on the
filesytem as cython_zstd ('-' -> '_'). Try to account for that.

Without the fix nxdbom breaks as

	ValueError: egg cython-zstd not found

nxdbom/__init__.py

@@ -185,7 +185,7 @@ def bom_software(installed_software_path): # -> {} (name,kind) -> PkgInfo
 
                 installed_eggs = [basename(_) for _ in (glob('%s/*.egg' % eggdir) +
                                                         glob('%s/*.egg' % eggdev))]
-                eggv = [_ for _ in installed_eggs if _.startswith('%s-' % eggname)]
+                eggv = [_ for _ in installed_eggs if _.lower().startswith('%s-' % eggcanon(eggname))]
                 if len(eggv) == 0:
                     raise ValueError('egg %s not found' % eggname)
                 if len(eggv) > 1:
@@ -224,6 +224,11 @@ def geturl(part, default=_missing):
 
 _egg_re = re.compile(r'^(?P<name>[\w\-\.]+)(\[.*\])?$')
 
+# eggcanon returns canonical name for an egg.
+# e.g. Cython-Zstd -> cython_zstd
+def eggcanon(eggname):
+    return eggname.lower().replace('-', '_')
+
 
 def bom_node(XXX):
     1/0

nxdbom/nxdbom_test.py

@@ -294,6 +294,32 @@ readline                     8.1        http://ftp.gnu.org/gnu/readline/readline
 readline5                    5.2        http://ftp.gnu.org/gnu/readline/readline-5.2.tar.gz
 """)
 
+# egg directoty on the filesystem might have different case and _ instead of -
+case1("""\
+[cython-zstd]
+recipe = zc.recipe.egg:custom
+egg = cython-zstd
+__buildout_installed__ = /ROOT/develop-eggs/cython_zstd-0.2-py2.7-linux-x86_64.egg
+
+[cython]
+recipe = zc.recipe.egg:custom
+egg = cython
+__buildout_installed__ = /Root/develop-eggs/Cython-0.29.24-py2.7-linux-x86_64.egg
+
+[neoppod]
+recipe = zc.recipe.egg
+_d = /ROOT/develop-eggs
+_e = /ROOT/eggs
+eggs = cython-zstd
+       cython
+-- /ROOT/develop-eggs/cython_zstd-0.2-py2.7-linux-x86_64.egg/x --
+-- /ROOT/develop-eggs/Cython-0.29.24-py2.7-linux-x86_64.egg/x --
+""", """
+>>> eggs:
+Cython                       0.29.24    https://pypi.org/project/Cython/0.29.24/
+cython_zstd                  0.2        https://pypi.org/project/cython_zstd/0.2/
+""")
+
 
 @pytest.mark.parametrize('build,bomok', testv)
 def test_bom_software(tmpdir, build, bomok):