Add MH and MALA MCMC examples (#251)

* Adding emcee example

* add discussion

* Add notebook to toc

* reduce emcee samples

* merge emcee example into NUTS example

* update comments in mcmc example

* change cell tags

* add tags to all tutorials

* add mala example to MCMC notebook

* filename change

* collapse chains into overlap with different colors

* fix filenames

docs/requirements.txt

@@ -1,3 +1,4 @@
+emcee
 ipywidgets
 jupyter-book
 matplotlib

docs/source/_toc.yml

@@ -21,11 +21,10 @@ chapters:
       - file: tutorials/InvertLensEquation
       - file: tutorials/Parameters
       - file: tutorials/Simulators
-      - file: tutorials/Playground
   - file: examples/index
     sections:
       - file: examples/Example_ImageFit_LM
-      - file: examples/Example_ImageFit_NUTS
+      - file: examples/Example_ImageFit_MCMC
       - file: examples/Example_QSOLensFit
   - file: contributing
   - file: frequently_asked_questions

docs/source/examples/Example_ImageFit_LM.ipynb

@@ -137,7 +137,11 @@
    "cell_type": "code",
    "execution_count": null,
    "id": "7",
-   "metadata": {},
+   "metadata": {
+    "tags": [
+     "hide-input"
+    ]
+   },
    "outputs": [],
    "source": [
     "# Generate the mock data\n",
@@ -242,7 +246,11 @@
    "cell_type": "code",
    "execution_count": null,
    "id": "10",
-   "metadata": {},
+   "metadata": {
+    "tags": [
+     "hide-input"
+    ]
+   },
    "outputs": [],
    "source": [
     "print(best_fit, allparams)\n",
@@ -310,7 +318,11 @@
    "cell_type": "code",
    "execution_count": null,
    "id": "14",
-   "metadata": {},
+   "metadata": {
+    "tags": [
+     "hide-cell"
+    ]
+   },
    "outputs": [],
    "source": [
     "def corner_plot_covariance(\n",