Merge branch 'master' of https://github.com/simpeg/simpegem into em/dev

Conflicts:
	.coveragerc
	.gitignore
	.travis.yml
	docs/api_Utils.rst
	docs/conf.py
	docs/index.rst
	requirements.txt
	setup.py

SimPEG/EM/Analytics/TDEM.py

@@ -0,0 +1,12 @@
+import numpy as np
+from scipy.constants import mu_0, pi
+from scipy.special import erf
+
+def hzAnalyticDipoleT(r, t, sigma):
+    theta = np.sqrt((sigma*mu_0)/(4*t))
+    tr = theta*r
+    etr = erf(tr)
+    t1 = (9/(2*tr**2) - 1)*etr
+    t2 = (1/np.sqrt(pi))*(9/tr + 4*tr)*np.exp(-tr**2)
+    hz = (t1 - t2)/(4*pi*r**3)
+    return hz