Pin NumPy to a version that doesn't break HDF5 loading

pandas-dev/pandas#24839

Author: reuben

requirements.txt

@@ -2,7 +2,7 @@ pandas
 progressbar2
 python-utils
 tensorflow == 1.12.0
-numpy
+numpy == 1.15.4
 matplotlib
 scipy
 sox

tc-train-tests.sh

@@ -53,7 +53,7 @@ decoder_pkg="ds_ctcdecoder-${whl_ds_version}-cp${pyver_pkg}-cp${pyver_pkg}${py_u
 
 decoder_pkg_url=${DECODER_ARTIFACTS_ROOT}/${decoder_pkg}
 
-LD_LIBRARY_PATH=${PY37_LDPATH}:$LD_LIBRARY_PATH pip install --verbose --only-binary :all: ${PY37_SOURCE_PACKAGE} --upgrade ${decoder_pkg_url} | cat
+LD_LIBRARY_PATH=${PY37_LDPATH}:$LD_LIBRARY_PATH pip install --verbose --only-binary :all: ${PY37_SOURCE_PACKAGE} ${decoder_pkg_url} | cat
 
 pushd ${HOME}/DeepSpeech/ds/
     # Run twice to test preprocessed features