fix Makefile ifdef & typo (#97)

Makefile

@@ -67,11 +67,11 @@ ifeq ($(USE_LLVM), 1)
 	CFLAGS += $(LLVM_INCLUDE) -DTVM_LLVM_VERSION=$(LLVM_VERSION)
 endif
 
-ifdef $(ADD_CFLAGS)
+ifdef ADD_CFLAGS
 	CFLAGS += $(ADD_CFLAGS)
 endif
 
-ifdef $(ADD_LDFLAGS)
+ifdef ADD_LDFLAGS
 	LDFLAGS += $(ADD_LDFLAGS)
 endif
 

docs/README.txt

 The documentation of tvm is generated with recommonmark and sphinx.
 
-- pip install sphinx sphinx-gallery sphinx_rtd_theme matplotlib Image recommonmark
+- pip install sphinx>=1.5.5 sphinx-gallery sphinx_rtd_theme matplotlib Image recommonmark
 - Build tvm first in the root folder.
 - You can build it locally by typing "make html" in this folder.

tutorials/python/get_started.py

@@ -139,7 +139,7 @@ np.testing.assert_allclose(c.asnumpy(), a.asnumpy() + b.asnumpy())
 # is a tvm Module. fadd is the host module that contains the host wrapper,
 # it also contains a device module for the CUDA function.
 #
-# The following code fetchs the device module and prints the content code.
+# The following code fetches the device module and prints the content code.
 #
 dev_module = fadd_cuda.imported_modules[0]
 print("-----CUDA code-----")