Update to styled-components v4

[hawkrives]

• styled-components@4
• use more css variables
• replace a number of pointless <div>s with Fragments
• replace font-feature-settings with font-variant
• replace Button with FlatButton/RaisedButton (and styled@4's as={Link} for link buttons)
• replace BlockIcon/InlineIcon with Icon

[buildsize]

File name	Previous Size	New Size	Change
404.html	861 bytes	861 bytes	0 bytes (0%)
app.css	90.73 KB	90.86 KB	129 bytes (0%)
app.js	994.45 KB	992.84 KB	-1.6 KB (0%)
areaData.url	50 bytes	50 bytes	0 bytes (0%)
chunk.area-editor.components.js	201.22 KB	201.49 KB	277 bytes (0%)
chunk.course-overlay.components.js	87.7 KB	87.78 KB	84 bytes (0%)
chunk.course-table.components.js	77.71 KB	77.44 KB	-284 bytes (0%)
chunk.degub.components.js	2.61 KB	2.61 KB	0 bytes (0%)
chunk.new-student.drive.component.js	1.46 KB	1.46 KB	0 bytes (0%)
chunk.new-student.import.component.js	19.74 KB	19.75 KB	11 bytes (0%)
chunk.new-student.manual.component.js	62.29 KB	62.29 KB	0 bytes (0%)
chunk.new-student.upload.component.js	33.58 KB	33.59 KB	7 bytes (0%)
chunk.search-sidebar.components.js	87.81 KB	87.89 KB	84 bytes (0%)
chunk.semester-detail.components.js	2.23 KB	2.23 KB	0 bytes (0%)
chunk.share-student.components.js	29.88 KB	29.88 KB	7 bytes (0%)
chunk.student.components.js	134.33 KB	133.05 KB	-1.29 KB (1%)
courseData.url	38 bytes	38 bytes	0 bytes (0%)
google04990d0c4887a5cd.html	53 bytes	53 bytes	0 bytes (0%)
index.html	636 bytes	636 bytes	0 bytes (0%)