Add colorcolumn option

Fixes #333

For example: `> set colorcolumn 80`.

runtime/colorschemes/atom-dark-tc.micro

@@ -17,3 +17,4 @@ color-link current-line-number "#656866,#1D1F21"
 color-link gutter-error "#FF4444,#1D1F21"
 color-link gutter-warning "#EEEE77,#1D1F21"
 color-link cursor-line "#2D2F31"
+color-link color-column "#2D2F31"

runtime/colorschemes/bubblegum.micro

@@ -17,3 +17,4 @@ color-link gutter-error "197,231"
 color-link gutter-warning "134,231"
 color-link line-number "246,254"
 color-link cursor-line "254"
+color-link color-column "254"

runtime/colorschemes/gruvbox.micro

@@ -13,3 +13,4 @@ color-link todo "bold 223,235"
 color-link line-number "243,237"
 color-link current-line-number "172,237"
 color-link cursor-line "237"
+color-link color-column "237"

runtime/colorschemes/monokai.micro

@@ -17,3 +17,4 @@ color-link current-line-number "#AAAAAA,#282828"
 color-link gutter-error "#CB4B16,#282828"
 color-link gutter-warning "#E6DB74,#282828"
 color-link cursor-line "#323232"
+color-link color-column "#323232"

runtime/colorschemes/simple.micro

@@ -14,3 +14,4 @@ color-link current-line-number "red"
 color-link gutter-error ",red"
 color-link gutter-warning "red"
 color-link cursor-line "white"
+color-link color-column "white"

runtime/colorschemes/solarized-tc.micro

@@ -16,3 +16,4 @@ color-link current-line-number "#586E75,#002833"
 color-link gutter-error "#003541,#CB4B16"
 color-link gutter-warning "#CB4B16,#002833"
 color-link cursor-line "#003541"
+color-link color-column "#003541"

runtime/colorschemes/solarized.micro

@@ -15,3 +15,4 @@ color-link current-line-number "brightgreen,default"
 color-link gutter-error "black,brightred"
 color-link gutter-warning "brightred,default"
 color-link cursor-line "black"
+color-link color-column "black"

runtime/colorschemes/zenburn.micro

@@ -17,4 +17,5 @@ color-link line-number "248,238"
 color-link gutter-error "237,174"
 color-link gutter-warning "174,237"
 color-link cursor-line "238"
+color-link color-column "238"
 color-link current-line-number "188,237"

runtime/help/colors.md

@@ -108,6 +108,8 @@ Here is a list of the colorscheme groups that you can use:
 * gutter-error
 * gutter-warning
 * cursor-line
+* current-line-number
+* color-column
 
 Colorschemes can be placed in the `~/.config/micro/colorschemes` directory to be used.
 

runtime/help/options.md

@@ -23,6 +23,11 @@ Here are the options that you can set:
     You can read more about micro's colorschemes in the `colors` help topic
     (`help colors`).
 
+* `colorcolumn`: if this is not set to 0, it will display a column at the specified
+   column. This is useful if you want column 80 to be highlighted special for example.
+
+	default value: `0`
+
 * `tabsize`: sets the tab size to `option`
 
 	default value: `4`